[GitHub] [kafka] mjsax commented on a diff in pull request #13188: KAFKA-14491: [5/N] Basic operations for RocksDB versioned store

["mjsax (via GitHub)" <gi...@apache.org>]

mjsax commented on code in PR #13188:
URL: https://github.com/apache/kafka/pull/13188#discussion_r1097979035


##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)

Review Comment:
   Should we specify what "now" is with regard to history retention time?



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}

Review Comment:
   ```suggestion
        * This operation is semantically equivalent to {@link #get(Object, long) #get(key, timestamp)}
   ```



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record
+     *         for this key as of the deletion timestamp is a tombstone, or
+     *         (3) the deletion timestamp is older than this store's history retention
+     *         (i.e., this store no longer contains data for the provided timestamp).
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    VersionedRecord<V> delete(K key, long timestamp);
+
+    /**
+     * Get the latest (by timestamp) record associated with this key.

Review Comment:
   "latest" -> "current"
   
   I think current is clearer, as it make it more "obvious" that the "latest" version might only be in the history?
   
   



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record
+     *         for this key as of the deletion timestamp is a tombstone, or
+     *         (3) the deletion timestamp is older than this store's history retention
+     *         (i.e., this store no longer contains data for the provided timestamp).
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    VersionedRecord<V> delete(K key, long timestamp);
+
+    /**
+     * Get the latest (by timestamp) record associated with this key.
+     *
+     * @param key The key to fetch
+     * @return The value and timestamp of the latest record associated with this key, or
+     *         {@code null} if either (1) the store contains no records for this key or (2) the
+     *         latest record for this key is a tombstone.

Review Comment:
   Case (1) and (2) sound "similar"... can we rephrase? The "is a tombstone" phrase sounds potentially confusing to users?
   
   maybe -> `or null if there is no current record for this key.` 



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);

Review Comment:
   nit (avoid abbreviations): `lvsName`



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record
+     *         for this key as of the deletion timestamp is a tombstone, or
+     *         (3) the deletion timestamp is older than this store's history retention
+     *         (i.e., this store no longer contains data for the provided timestamp).
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    VersionedRecord<V> delete(K key, long timestamp);
+
+    /**
+     * Get the latest (by timestamp) record associated with this key.
+     *
+     * @param key The key to fetch
+     * @return The value and timestamp of the latest record associated with this key, or
+     *         {@code null} if either (1) the store contains no records for this key or (2) the
+     *         latest record for this key is a tombstone.
+     * @throws NullPointerException       If null is used for key.
+     * @throws InvalidStateStoreException if the store is not initialized
+     */
+    VersionedRecord<V> get(K key);
+
+    /**
+     * Get the latest record associated with this key with timestamp not exceeding the specified
+     * timestamp bound.

Review Comment:
   > with timestamp not exceeding the specified timestamp bound.
   
   Sound complicated... maybe -> `Get the latest record associated with this key and timestamp.`



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(

Review Comment:
   Why do we need this helper -- seems it only called once. Can we inline it? The calling method is basically empty.



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
+                    );
+                } else {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(null, timestamp, foundTs).serialize()
+                    );
+                }
+            } else {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // insert as latest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(timestamp, foundTs, value);
+                    segment.put(key, sv.serialize());
+                } else {
+                    // insert as earliest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsEarliest(timestamp, value);
+                    segment.put(key, sv.serialize());
+                }
+            }
+        }
+    }
+
+    /**
+     * Bytes layout for the value portion of rows stored in the latest value store. The layout is
+     * a fixed-size timestamp concatenated with the actual record value.
+     */
+    static class LatestValueSchema {
+
+        private static final int TIMESTAMP_SIZE = 8;
+
+        /**
+         * @return the timestamp, from the latest value store value bytes
+         */
+        long getTimestamp(final byte[] latestValue) {
+            return ByteBuffer.wrap(latestValue).getLong();
+        }
+
+        /**
+         * @return the actual record value, from the latest value store value bytes
+         */
+        byte[] getValue(final byte[] latestValue) {
+            final byte[] value = new byte[latestValue.length - TIMESTAMP_SIZE];
+            System.arraycopy(latestValue, TIMESTAMP_SIZE, value, 0, value.length);
+            return value;
+        }
+
+        /**
+         * @return the formatted bytes containing the provided {@code value} and {@code timestamp},
+         *         ready to be stored into the latest value store
+         */
+        byte[] from(final byte[] value, final long timestamp) {
+            if (value == null) {
+                throw new IllegalStateException("Cannot store tombstone in latest value");
+            }
+
+            return ByteBuffer.allocate(TIMESTAMP_SIZE + value.length)
+                .putLong(timestamp)
+                .put(value)
+                .array();
+        }
+    }
+
+    /**
+     * Bytes layout for the value portion of rows stored in the segments stores. This is a simple
+     * wrapper class for the static methods provided by {@link RocksDBVersionedStoreSegmentValueFormatter}.
+     * See the javadocs in {@link RocksDBVersionedStoreSegmentValueFormatter} for more.
+     */
+    static class SegmentValueSchema {

Review Comment:
   Not sure what value we get from this class?



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete

Review Comment:
   Kafka has an implicit contract that `null` objects must be serialized to `null` bytes[] (for "plain" Kafka the impact of not following this contract is smaller, but for KS we would "fall apart" if the contract is violated.
   
   We should just say, "can be null; null is treated as delete".



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.

Review Comment:
   ```suggestion
        * Add a new record version for the specified timestamp associated with this key.
   ```



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),

Review Comment:
   Why do we pass an optional?



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of

Review Comment:
   I would simplify: case (1) and (2) is basically the same -- "is a tombstone" is a weird formulation IMHO.
   
   `or {@code null} if no record for this key exist at the specified timestamp (note: this includes the case if the timestamp is older than history retention time).`



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record
+     *         for this key as of the deletion timestamp is a tombstone, or
+     *         (3) the deletion timestamp is older than this store's history retention
+     *         (i.e., this store no longer contains data for the provided timestamp).
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    VersionedRecord<V> delete(K key, long timestamp);
+
+    /**
+     * Get the latest (by timestamp) record associated with this key.
+     *
+     * @param key The key to fetch
+     * @return The value and timestamp of the latest record associated with this key, or
+     *         {@code null} if either (1) the store contains no records for this key or (2) the
+     *         latest record for this key is a tombstone.
+     * @throws NullPointerException       If null is used for key.
+     * @throws InvalidStateStoreException if the store is not initialized

Review Comment:
   This one is missing in `put()` and `delete()` above -- seems we also don't have this documented on every method on `KeyValueStore`...
   
   Maybe we should do a follow up PR to check all existing interfaces if the do document this exception?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);

Review Comment:
   It's hard to keep track of what it what... (everything has "value" in it's name...) this is the full "row" for a segment now, right?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(

Review Comment:
   "fall through" is not very descriptive -- can we find a better name?
   
   I needed to hop between the different method implementation to understand the code. The control flow is not easy (not sure if/how we could improve it right now...)



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record
+     *         for this key as of the deletion timestamp is a tombstone, or
+     *         (3) the deletion timestamp is older than this store's history retention
+     *         (i.e., this store no longer contains data for the provided timestamp).
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    VersionedRecord<V> delete(K key, long timestamp);
+
+    /**
+     * Get the latest (by timestamp) record associated with this key.
+     *
+     * @param key The key to fetch
+     * @return The value and timestamp of the latest record associated with this key, or
+     *         {@code null} if either (1) the store contains no records for this key or (2) the
+     *         latest record for this key is a tombstone.
+     * @throws NullPointerException       If null is used for key.
+     * @throws InvalidStateStoreException if the store is not initialized
+     */
+    VersionedRecord<V> get(K key);
+
+    /**
+     * Get the latest record associated with this key with timestamp not exceeding the specified
+     * timestamp bound.
+     *
+     * @param key           The key to fetch
+     * @param asOfTimestamp The timestamp bound. This bound is inclusive; if a record
+     *                      (for the specified key) exists with this timestamp, then
+     *                      this is the record that will be returned.
+     * @return The value and timestamp of the latest record associated with this key
+     *         satisfying the provided timestamp bound, or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record

Review Comment:
   cf comment on `delete()`



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedRecord.java:
##########
@@ -0,0 +1,74 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.KeyValue;
+
+import java.util.Objects;
+
+/**
+ * Combines a value from a {@link KeyValue} with a timestamp, for use as the return type

Review Comment:
   Well, we don't know how `VersionedRecord` is really used, do we? So the reference to `KeyValue` is a little odd?



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of
+     *         (1) the store contains no records for this key, (2) the latest record
+     *         for this key as of the deletion timestamp is a tombstone, or
+     *         (3) the deletion timestamp is older than this store's history retention
+     *         (i.e., this store no longer contains data for the provided timestamp).
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    VersionedRecord<V> delete(K key, long timestamp);
+
+    /**
+     * Get the latest (by timestamp) record associated with this key.
+     *
+     * @param key The key to fetch
+     * @return The value and timestamp of the latest record associated with this key, or

Review Comment:
   latest -> current?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs

Review Comment:
   This comment is misleading, as we still might to put into "latest value store" inside `putFallThrough`



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(

Review Comment:
   `putLatestValueStore` -> `maybePutLatestValueStore`



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(

Review Comment:
   `maybePutSegments`



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp

Review Comment:
   We not just do this optimization right away?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();

Review Comment:
   I think this needs explanation. We use `timestamp` in the line above as "validTo" for existing records (well, think it could only be a single one; if yes, maybe add comment about it), right? That's why we need to move the "oldest" record in the segment we insert into, one segment back, as is validTo could be reduced by the put() ?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {

Review Comment:
   Not sure what value this interface adds? Are you trying to hide other methods from `LogicalKeyValueSegment`? If yes, why? -- We usually only add a new interface if there is clear value to not introduce unnecessary boilerplate. 



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);

Review Comment:
   This is confusing... We pass in a `segmentValue` (which is bytes[] but I needed to double check) to get back a `SegmentValue` object. (Too many thing with the same name)
   
   In other stores, we use `V value` for the deserialized object and `byte[] rawValue` for the serialized bytes. Can we apply the same (or similar) naming pattern to make easier to read (we also run out of name here and you start to be "creative" using `sv`... -- as always, avoid abbreviations)



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);

Review Comment:
   passing `writeToOlderSegmentNeeded` might be unclear (I understand it)... not sure if could make it cleaner? Better variable name? (or add a comment)



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {

Review Comment:
   The control flow is hard to follow due to nesting... What about this:
   
   (1) rename `writeToOlderSegmentNeeded` to `includeValue` (and explain in a comment why we need to include it.
   (2) return directly inside if-blocks to avoid `else` and nesting:
   ```
   if (searchResult.validFrom() == timestamp) {
     ...
     return PutStatus(true, foundTs);
   }
   
   if (includeValue) { // we included a value and thus need to move to older segment plus update found segment
   
     return PutStatus(true, foundTs);
   }
   
   // just plain insert into found segment
   sv.insert(timestamp, value, searchResult.index());
   segment.put(key, sv.serialize());
   return PutStatus(true, foundTs);
   ```
   
   



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {

Review Comment:
   What value does this class add? Seems it's just boilerplate?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.

Review Comment:
   This part is long enough to go into a helper method?



##########
streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java:
##########
@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+
+/**
+ * A key-value store that stores multiple record versions per key, and supports timestamp-based
+ * retrieval operations to return the latest record (per key) as of a specified timestamp.
+ * Only one record is stored per key and timestamp, i.e., a second call to
+ * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first.
+ * <p>
+ * Each store instance has an associated, fixed-duration "history retention" which specifies
+ * how long old record versions should be kept for. In particular, a versioned store guarantees
+ * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp
+ * bound is within history retention of the current observed stream time. (Queries with timestamp
+ * bound older than the specified history retention are considered invalid.)
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public interface VersionedKeyValueStore<K, V> extends StateStore {
+
+    /**
+     * Add a new record version associated with this key.
+     *
+     * @param key       The key
+     * @param value     The value, it can be {@code null};
+     *                  if the serialized bytes are also {@code null} it is interpreted as a delete
+     * @param timestamp The timestamp for this record version
+     * @throws NullPointerException If {@code null} is used for key.
+     */
+    void put(K key, V value, long timestamp);
+
+    /**
+     * Delete the value associated with this key from the store, at the specified timestamp
+     * (if there is such a value), and return the deleted value.
+     * <p>
+     * This operation is semantically equivalent to {@link #get(Object, long)} #get(key, timestamp))}
+     * followed by {@link #put(Object, Object, long) #put(key, null, timestamp)}.
+     *
+     * @param key       The key
+     * @param timestamp The timestamp for this delete
+     * @return The value and timestamp of the latest record associated with this key
+     *         as of the deletion timestamp (inclusive), or {@code null} if any of

Review Comment:
   Also add something like this?
   
   `Note: the record timestamp {@code r.ts} of the returned {@link VersionedRecord} may be smaller than the provided delete timestamp.`



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;

Review Comment:
   It seems unnecessary to pass in `prevFoundTs` as it will always be the sentinel.



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {

Review Comment:
   For this case `writeToOlderSegmentNeeded` is voided, indicating that we picked a "bad" variable name?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);

Review Comment:
   `latestValue` -> `latestValueAndTimestamp`



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {

Review Comment:
   The control flow is tricky here (I only understood after reading much more code).
   
   Add comment what `segment == null` implies (and why we don't update the "drop record sensor")



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.

Review Comment:
   Why not apply this optimization?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this

Review Comment:
   "earlier segment" -> or "latest value store", right?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);

Review Comment:
   `valueToMove` -> `rawValueToMove` (ie, w/o timestamp)?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(

Review Comment:
   Why is this method static? If forces us to have a long parameter list.



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
+                    );
+                } else {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(null, timestamp, foundTs).serialize()
+                    );
+                }
+            } else {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {

Review Comment:
   I am just wondering if this case is actually possible? Above you just say vaguely `depending on the circumstances of the fall-through` -- can you elaborate?
   
   The only case for "latest" is do understand would be the case when we actually insert into the "latest value store" instead of a segment. If we really insert into a segment, it seems we would always insert as earliest?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise

Review Comment:
   This comment about "why not middle" is gold! Thanks.



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
+                    );
+                } else {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(null, timestamp, foundTs).serialize()
+                    );
+                }
+            } else {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // insert as latest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(timestamp, foundTs, value);
+                    segment.put(key, sv.serialize());
+                } else {
+                    // insert as earliest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsEarliest(timestamp, value);
+                    segment.put(key, sv.serialize());
+                }
+            }
+        }
+    }
+
+    /**
+     * Bytes layout for the value portion of rows stored in the latest value store. The layout is
+     * a fixed-size timestamp concatenated with the actual record value.
+     */
+    static class LatestValueSchema {
+
+        private static final int TIMESTAMP_SIZE = 8;
+
+        /**
+         * @return the timestamp, from the latest value store value bytes
+         */
+        long getTimestamp(final byte[] latestValue) {
+            return ByteBuffer.wrap(latestValue).getLong();
+        }
+
+        /**
+         * @return the actual record value, from the latest value store value bytes
+         */
+        byte[] getValue(final byte[] latestValue) {

Review Comment:
   `latestValue` -> `latestValueAndTimestamp` ?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(

Review Comment:
   Why `static` ?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
+                    );
+                } else {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(null, timestamp, foundTs).serialize()
+                    );
+                }
+            } else {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // insert as latest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(timestamp, foundTs, value);
+                    segment.put(key, sv.serialize());
+                } else {
+                    // insert as earliest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsEarliest(timestamp, value);
+                    segment.put(key, sv.serialize());
+                }
+            }
+        }
+    }
+
+    /**
+     * Bytes layout for the value portion of rows stored in the latest value store. The layout is
+     * a fixed-size timestamp concatenated with the actual record value.
+     */
+    static class LatestValueSchema {
+
+        private static final int TIMESTAMP_SIZE = 8;
+
+        /**
+         * @return the timestamp, from the latest value store value bytes
+         */
+        long getTimestamp(final byte[] latestValue) {

Review Comment:
   `latestValue` -> `latestValueAndTimestamp` ?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {

Review Comment:
   Why do we need this `if`? Seems we can just do
   ```
   segment.put(
     key,
     segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
   );
   ```
   
   If `value == null`, we still pass `null` as first argument.



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
+                    );
+                } else {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(null, timestamp, foundTs).serialize()
+                    );
+                }
+            } else {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // insert as latest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(timestamp, foundTs, value);
+                    segment.put(key, sv.serialize());
+                } else {
+                    // insert as earliest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsEarliest(timestamp, value);
+                    segment.put(key, sv.serialize());
+                }
+            }
+        }
+    }
+
+    /**
+     * Bytes layout for the value portion of rows stored in the latest value store. The layout is
+     * a fixed-size timestamp concatenated with the actual record value.
+     */
+    static class LatestValueSchema {

Review Comment:
   Seems everything in this class could be static methods? If yes, we would not need to have an instance at hand and can eliminate a class member variable.



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(

Review Comment:
   "fall through" is not very descriptive -- can we find a better name?
   
   I needed to hop between the different method implementation to understand the code. The control flow is not easy (not sure if/how we could improve it right now...)



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {
+                                final byte[] olderSegmentValue = olderSegment.get(key);
+                                if (olderSegmentValue == null) {
+                                    olderSegment.put(
+                                        key,
+                                        segmentValueSchema.newSegmentValueWithRecord(
+                                            searchResult.value(), searchResult.validFrom(), timestamp
+                                        ).serialize()
+                                    );
+                                } else {
+                                    final SegmentValue olderSv = segmentValueSchema.deserialize(olderSegmentValue);
+                                    olderSv.insertAsLatest(searchResult.validFrom(), timestamp, searchResult.value());
+                                    olderSegment.put(key, olderSv.serialize());
+                                }
+                            }
+
+                            // update in newer segment (replace the record that was just moved with the new one)
+                            sv.updateRecord(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        } else {
+                            sv.insert(timestamp, value, searchResult.index());
+                            segment.put(key, sv.serialize());
+                        }
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                if (foundMinTs < observedStreamTime - historyRetention) {
+                    // the record being inserted does not affect version history. discard and return
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return new PutStatus(true, foundTs);
+                }
+
+                // it's possible the record belongs in this segment, but also possible it belongs
+                // in an earlier segment. mark as tentative and continue. as an optimization, this
+                // code could be updated to skip forward to the segment containing foundMinTs.
+                foundTs = foundMinTs;
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> void putFallThrough(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long foundTs
+    ) {
+        if (foundTs == SENTINEL_TIMESTAMP) {
+            // insert into latest value store
+            if (value != null) {
+                versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+            } else {
+                // tombstones are not inserted into the latest value store. insert into segment instead.
+                // the specific segment to insert to is determined based on the tombstone's timestamp
+                final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                    versionedStoreClient.segmentIdForTimestamp(timestamp), context, observedStreamTime);
+                if (segment == null) {
+                    if (expiredRecordSensor.isPresent()) {
+                        expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                        LOG.warn("Skipping record for expired put.");
+                    }
+                    return;
+                }
+
+                final byte[] segmentValue = segment.get(key);
+                if (segmentValue == null) {
+                    // in this special case where the latest record version (for a particular key)
+                    // is a tombstone, and the segment that the tombstone belongs in contains no
+                    // record versions for this key, create a new "degenerate" segment with the
+                    // tombstone's timestamp as both validFrom and validTo timestamps for the segment
+                    segment.put(key, segmentValueSchema.newSegmentValueWithRecord(null, timestamp, timestamp).serialize());
+                } else {
+                    // insert as latest, since foundTs = sentinel means nothing later exists
+                    if (segmentValueSchema.getNextTimestamp(segmentValue) == timestamp) {
+                        // next timestamp equal to put() timestamp already represents a tombstone,
+                        // so no additional insertion is needed in this case
+                        return;
+                    }
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(
+                        segmentValueSchema.getNextTimestamp(segmentValue),
+                        timestamp,
+                        null
+                    );
+                    segment.put(key, sv.serialize());
+                }
+            }
+        } else {
+            // insert into segment corresponding to foundTs, as foundTs represents the validTo
+            // timestamp of the current put.
+            // the new record is either the earliest or the latest in this segment, depending on the
+            // circumstances of the fall-through. (it cannot belong in the middle because otherwise
+            // putSegments() above would have identified a segment for which
+            // minTimestamp <= timestamp < nextTimestamp, and putSegments would've completed the
+            // put procedure without reaching this fall-through case.)
+            final T segment = versionedStoreClient.getOrCreateSegmentIfLive(
+                versionedStoreClient.segmentIdForTimestamp(foundTs), context, observedStreamTime);
+            if (segment == null) {
+                if (expiredRecordSensor.isPresent()) {
+                    expiredRecordSensor.get().record(1.0d, ProcessorContextUtils.currentSystemTime(context));
+                    LOG.warn("Skipping record for expired put.");
+                }
+                return;
+            }
+
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue == null) {
+                if (value != null) {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(value, timestamp, foundTs).serialize()
+                    );
+                } else {
+                    segment.put(
+                        key,
+                        segmentValueSchema.newSegmentValueWithRecord(null, timestamp, foundTs).serialize()
+                    );
+                }
+            } else {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // insert as latest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsLatest(timestamp, foundTs, value);
+                    segment.put(key, sv.serialize());
+                } else {
+                    // insert as earliest
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    sv.insertAsEarliest(timestamp, value);
+                    segment.put(key, sv.serialize());
+                }
+            }
+        }
+    }
+
+    /**
+     * Bytes layout for the value portion of rows stored in the latest value store. The layout is
+     * a fixed-size timestamp concatenated with the actual record value.
+     */
+    static class LatestValueSchema {

Review Comment:
   `LatestValueSchema` -> `LatestValueFormatter` ?



##########
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBVersionedStore.java:
##########
@@ -0,0 +1,792 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.state.internals;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextUtils;
+import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
+import org.apache.kafka.streams.processor.internals.StoreToProcessorContextAdapter;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue;
+import org.apache.kafka.streams.state.internals.RocksDBVersionedStoreSegmentValueFormatter.SegmentValue.SegmentSearchResult;
+import org.apache.kafka.streams.state.internals.metrics.RocksDBMetricsRecorder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A persistent, versioned key-value store based on RocksDB.
+ * <p>
+ * This store implementation consists of a "latest value store" and "segment stores." The latest
+ * record version for each key is stored in the latest value store, while older record versions
+ * are stored in the segment stores. Conceptually, each record version has two associated
+ * timestamps:
+ * <ul>
+ *     <li>a {@code validFrom} timestamp. This timestamp is explicitly associated with the record
+ *     as part of the {@link VersionedKeyValueStore#put(Object, Object, long)}} call to the store;
+ *     i.e., this is the record's timestamp.</li>
+ *     <li>a {@code validTo} timestamp. This is the timestamp of the next record (or deletion)
+ *     associated with the same key, and is implicitly associated with the record. This timestamp
+ *     can change as new records are inserted into the store.</li>
+ * </ul>
+ * The validity interval of a record is from validFrom (inclusive) to validTo (exclusive), and
+ * can change as new record versions are inserted into the store (and validTo changes as a result).
+ * <p>
+ * Old record versions are stored in segment stores according to their validTo timestamps. This
+ * allows for efficient expiry of old record versions, as entire segments can be dropped from the
+ * store at a time, once the records contained in the segment are no longer relevant based on the
+ * store's history retention (for an explanation of "history retention", see
+ * {@link VersionedKeyValueStore}). Multiple record versions (for the same key) within a single
+ * segment are stored together using the format specified in {@link RocksDBVersionedStoreSegmentValueFormatter}.
+ */
+public class RocksDBVersionedStore implements VersionedKeyValueStore<Bytes, byte[]> {
+    private static final Logger LOG = LoggerFactory.getLogger(RocksDBVersionedStore.class);
+    // a marker to indicate that no record version has yet been found as part of an ongoing
+    // put() procedure. any value which is not a valid record timestamp will do.
+    private static final long SENTINEL_TIMESTAMP = Long.MIN_VALUE;
+
+    private final String name;
+    private final long historyRetention;
+    private final RocksDBMetricsRecorder metricsRecorder;
+
+    private final RocksDBStore latestValueStore;
+    private final LogicalKeyValueSegments segmentStores;
+    private final LatestValueSchema latestValueSchema;
+    private final SegmentValueSchema segmentValueSchema;
+    private final VersionedStoreClient<LogicalKeyValueSegment> versionedStoreClient;
+
+    private ProcessorContext context;
+    private StateStoreContext stateStoreContext;
+    private Sensor expiredRecordSensor;
+    private long observedStreamTime = ConsumerRecord.NO_TIMESTAMP;
+    private Position position;
+    private OffsetCheckpoint positionCheckpoint;
+    private volatile boolean open;
+
+    RocksDBVersionedStore(final String name, final String metricsScope, final long historyRetention, final long segmentInterval) {
+        this.name = name;
+        this.historyRetention = historyRetention;
+        this.metricsRecorder = new RocksDBMetricsRecorder(metricsScope, name);
+        this.latestValueStore = new RocksDBStore(lvsName(name), name, metricsRecorder);
+        this.segmentStores = new LogicalKeyValueSegments(segmentsName(name), name, historyRetention, segmentInterval, metricsRecorder);
+        this.latestValueSchema = new LatestValueSchema();
+        this.segmentValueSchema = new SegmentValueSchema();
+        this.versionedStoreClient = new RocksDBVersionedStoreClient();
+    }
+
+    @Override
+    public void put(final Bytes key, final byte[] value, final long timestamp) {
+
+        doPut(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            Optional.of(expiredRecordSensor),
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp
+        );
+
+        observedStreamTime = Math.max(observedStreamTime, timestamp);
+    }
+
+    @Override
+    public VersionedRecord<byte[]> delete(final Bytes key, final long timestamp) {
+        final VersionedRecord<byte[]> existingRecord = get(key, timestamp);
+        put(key, null, timestamp);
+        return existingRecord;
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key) {
+        // latest value (if present) is guaranteed to be in the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            return new VersionedRecord<>(
+                latestValueSchema.getValue(latestValue),
+                latestValueSchema.getTimestamp(latestValue)
+            );
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public VersionedRecord<byte[]> get(final Bytes key, final long asOfTimestamp) {
+
+        if (asOfTimestamp < observedStreamTime - historyRetention) {
+            // history retention has elapsed. return null for predictability, even if data
+            // is still present in store.
+            return null;
+        }
+
+        // first check the latest value store
+        final byte[] latestValue = latestValueStore.get(key);
+        if (latestValue != null) {
+            final long latestTimestamp = latestValueSchema.getTimestamp(latestValue);
+            if (latestTimestamp <= asOfTimestamp) {
+                return new VersionedRecord<>(latestValueSchema.getValue(latestValue), latestTimestamp);
+            }
+        }
+
+        // check segment stores
+        final List<LogicalKeyValueSegment> segments = segmentStores.segments(asOfTimestamp, Long.MAX_VALUE, false);
+        for (final LogicalKeyValueSegment segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long nextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (nextTs <= asOfTimestamp) {
+                    // this segment contains no data for the queried timestamp, so earlier segments
+                    // cannot either
+                    return null;
+                }
+
+                if (segmentValueSchema.getMinTimestamp(segmentValue) > asOfTimestamp) {
+                    // the segment only contains data for after the queried timestamp. skip and
+                    // continue the search to earlier segments. as an optimization, this code
+                    // could be updated to skip forward to the segment containing the minTimestamp
+                    // in the if-condition above.
+                    continue;
+                }
+
+                // the desired result is contained in this segment
+                final SegmentSearchResult searchResult =
+                    segmentValueSchema.deserialize(segmentValue).find(asOfTimestamp, true);
+                if (searchResult.value() != null) {
+                    return new VersionedRecord<>(searchResult.value(), searchResult.validFrom());
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        // checked all segments and no results found
+        return null;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public void flush() {
+        // order shouldn't matter since failure to flush is a fatal exception
+        segmentStores.flush();
+        latestValueStore.flush();
+    }
+
+    @Override
+    public void close() {
+        open = false;
+
+        // close latest value store first so that calls to get() immediately begin to fail with
+        // store not open, as all calls to get() first get() from latest value store
+        latestValueStore.close();
+        segmentStores.close();
+    }
+
+    @Override
+    public boolean persistent() {
+        return true;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return open;
+    }
+
+    @Override
+    public Position getPosition() {
+        return position;
+    }
+
+    @Deprecated
+    @Override
+    public void init(final ProcessorContext context, final StateStore root) {
+        this.context = context;
+
+        final StreamsMetricsImpl metrics = ProcessorContextUtils.getMetricsImpl(context);
+        final String threadId = Thread.currentThread().getName();
+        final String taskName = context.taskId().toString();
+
+        expiredRecordSensor = TaskMetrics.droppedRecordsSensor(
+            threadId,
+            taskName,
+            metrics
+        );
+
+        metricsRecorder.init(ProcessorContextUtils.getMetricsImpl(context), context.taskId());
+
+        latestValueStore.openDB(context.appConfigs(), context.stateDir());
+        segmentStores.openExisting(context, observedStreamTime);
+
+        final File positionCheckpointFile = new File(context.stateDir(), name() + ".position");
+        this.positionCheckpoint = new OffsetCheckpoint(positionCheckpointFile);
+        this.position = StoreQueryUtils.readPositionFromCheckpoint(positionCheckpoint);
+
+        // register and possibly restore the state from the logs
+        stateStoreContext.register(
+            root,
+            (RecordBatchingStateRestoreCallback) RocksDBVersionedStore.this::restoreBatch,
+            () -> StoreQueryUtils.checkpointPosition(positionCheckpoint, position)
+        );
+
+        open = true;
+    }
+
+    @Override
+    public void init(final StateStoreContext context, final StateStore root) {
+        this.stateStoreContext = context;
+        init(StoreToProcessorContextAdapter.adapt(context), root);
+    }
+
+    // VisibleForTesting
+    void restoreBatch(final Collection<ConsumerRecord<byte[], byte[]>> records) {
+        throw new UnsupportedOperationException("not yet implemented");
+    }
+
+    /**
+     * Generic interface for segment stores. See {@link VersionedStoreClient} for use.
+     */
+    interface VersionedStoreSegment {
+
+        /**
+         * @return segment id
+         */
+        long id();
+
+        void put(Bytes key, byte[] value);
+
+        byte[] get(Bytes key);
+    }
+
+    /**
+     * Extracts all operations required for writing to the versioned store (via
+     * {@link #put(Bytes, byte[], long)}) into a generic client interface, so that the same
+     * {@code put(...)} logic can be shared during regular store operation and during restore.
+     *
+     * @param <T> the segment type used by this client
+     */
+    interface VersionedStoreClient<T extends VersionedStoreSegment> {
+
+        /**
+         * @return the contents of the latest value store, for the given key
+         */
+        byte[] getLatestValue(Bytes key);
+
+        /**
+         * Puts the provided key and value into the latest value store.
+         */
+        void putLatestValue(Bytes key, byte[] value);
+
+        /**
+         * Deletes the existing value (if any) from the latest value store, for the given key.
+         */
+        void deleteLatestValue(Bytes key);
+
+        /**
+         * @return the segment with the provided id, or {@code null} if the segment is expired
+         */
+        T getOrCreateSegmentIfLive(long segmentId, ProcessorContext context, long streamTime);
+
+        /**
+         * @return all segments in the store which contain timestamps at least the provided
+         *         timestamp bound, in reverse order by segment id (and time), i.e., such that
+         *         the most recent segment is first
+         */
+        List<T> getReverseSegments(long timestampFrom);
+
+        /**
+         * @return the segment id associated with the provided timestamp
+         */
+        long segmentIdForTimestamp(long timestamp);
+    }
+
+    /**
+     * Client for writing into (and reading from) this persistent {@link RocksDBVersionedStore}.
+     */
+    private class RocksDBVersionedStoreClient implements VersionedStoreClient<LogicalKeyValueSegment> {
+
+        @Override
+        public byte[] getLatestValue(final Bytes key) {
+            return latestValueStore.get(key);
+        }
+
+        @Override
+        public void putLatestValue(final Bytes key, final byte[] value) {
+            latestValueStore.put(key, value);
+        }
+
+        @Override
+        public void deleteLatestValue(final Bytes key) {
+            latestValueStore.delete(key);
+        }
+
+        @Override
+        public LogicalKeyValueSegment getOrCreateSegmentIfLive(final long segmentId, final ProcessorContext context, final long streamTime) {
+            return segmentStores.getOrCreateSegmentIfLive(segmentId, context, streamTime);
+        }
+
+        @Override
+        public List<LogicalKeyValueSegment> getReverseSegments(final long timestampFrom) {
+            return segmentStores.segments(timestampFrom, Long.MAX_VALUE, false);
+        }
+
+        @Override
+        public long segmentIdForTimestamp(final long timestamp) {
+            return segmentStores.segmentId(timestamp);
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> void doPut(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp
+    ) {
+        // track the smallest timestamp seen so far that is larger than insertion timestamp.
+        // this timestamp determines, based on all segments searched so far, which segment the
+        // new record should be inserted into. the starting "sentinel timestamp" represents
+        // that the segment should be inserted into the latest value store.
+        long foundTs = SENTINEL_TIMESTAMP;
+
+        // check latest value store
+        PutStatus status = putLatestValueStore(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // continue search in segments
+        status = putSegments(
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            historyRetention,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+        if (status.isComplete) {
+            return;
+        } else {
+            foundTs = status.foundTs;
+        }
+
+        // ran out of segments to search. insert into segment as specified by foundTs
+        putFallThrough(
+            latestValueSchema,
+            segmentValueSchema,
+            versionedStoreClient,
+            expiredRecordSensor,
+            context,
+            observedStreamTime,
+            key,
+            value,
+            timestamp,
+            foundTs
+        );
+    }
+
+    /**
+     * Represents the status of an ongoing put() operation.
+     */
+    private static class PutStatus {
+
+        /**
+         * Whether the put() call has been completed.
+         */
+        final boolean isComplete;
+
+        /**
+         * The smallest timestamp seen so far, as part of this current put() operation, that is
+         * larger than insertion timestamp. This timestamp determines, based on all segments
+         * searched so far, which segment the new record should be inserted into.
+         */
+        final long foundTs;
+
+        PutStatus(final boolean isComplete, final long foundTs) {
+            this.isComplete = isComplete;
+            this.foundTs = foundTs;
+        }
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putLatestValueStore(
+        final LatestValueSchema latestValueSchema,
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final byte[] latestValue = versionedStoreClient.getLatestValue(key);
+        if (latestValue != null) {
+            foundTs = latestValueSchema.getTimestamp(latestValue);
+            if (timestamp >= foundTs) {
+                // new record belongs in the latest value store
+                if (timestamp > foundTs) {
+                    // move existing latest value into segment.
+                    // it's important that this step happens before the update to the latest value
+                    // store. if there is a partial failure (this step succeeds but the update to
+                    // the latest value store fails), updating the segment first means there will
+                    // not be data loss. (rather, there will be duplicated data which is fine as
+                    // it can/will be reconciled later.)
+                    final long segmentId = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final T segment = versionedStoreClient.getOrCreateSegmentIfLive(segmentId, context, observedStreamTime);
+                    if (segment != null) {
+                        final byte[] valueToMove = latestValueSchema.getValue(latestValue);
+                        final byte[] segmentValueBytes = segment.get(key);
+                        if (segmentValueBytes == null) {
+                            segment.put(
+                                key,
+                                segmentValueSchema
+                                    .newSegmentValueWithRecord(valueToMove, foundTs, timestamp)
+                                    .serialize()
+                            );
+                        } else {
+                            final SegmentValue segmentValue = segmentValueSchema.deserialize(segmentValueBytes);
+                            segmentValue.insertAsLatest(foundTs, timestamp, valueToMove);
+                            segment.put(key, segmentValue.serialize());
+                        }
+                    }
+                }
+
+                // update latest value store
+                if (value != null) {
+                    versionedStoreClient.putLatestValue(key, latestValueSchema.from(value, timestamp));
+                } else {
+                    versionedStoreClient.deleteLatestValue(key);
+                }
+                return new PutStatus(true, foundTs);
+            }
+        }
+        return new PutStatus(false, foundTs);
+    }
+
+    private static <T extends VersionedStoreSegment> PutStatus putSegments(
+        final SegmentValueSchema segmentValueSchema,
+        final VersionedStoreClient<T> versionedStoreClient,
+        final Optional<Sensor> expiredRecordSensor,
+        final ProcessorContext context,
+        final long observedStreamTime,
+        final long historyRetention,
+        final Bytes key,
+        final byte[] value,
+        final long timestamp,
+        final long prevFoundTs
+    ) {
+        // initialize with current foundTs value
+        long foundTs = prevFoundTs;
+
+        final List<T> segments = versionedStoreClient.getReverseSegments(timestamp);
+        for (final T segment : segments) {
+            final byte[] segmentValue = segment.get(key);
+            if (segmentValue != null) {
+                final long foundNextTs = segmentValueSchema.getNextTimestamp(segmentValue);
+                if (foundNextTs <= timestamp) {
+                    // this segment (and all earlier segments) does not contain records affected by
+                    // this put. insert into the segment specified by foundTs (i.e., the next
+                    // phase of the put() procedure) and conclude the procedure.
+                    return new PutStatus(false, foundTs);
+                }
+
+                final long foundMinTs = segmentValueSchema.getMinTimestamp(segmentValue);
+                if (foundMinTs <= timestamp) {
+                    // the record being inserted belongs in this segment.
+                    // insert and conclude the procedure.
+                    final long segmentIdForTimestamp = versionedStoreClient.segmentIdForTimestamp(timestamp);
+                    final boolean writeToOlderSegmentNeeded = segmentIdForTimestamp != segment.id();
+
+                    final SegmentValue sv = segmentValueSchema.deserialize(segmentValue);
+                    final SegmentSearchResult searchResult = sv.find(timestamp, writeToOlderSegmentNeeded);
+
+                    if (searchResult.validFrom() == timestamp) {
+                        // this put() replaces an existing entry, rather than adding a new one
+                        sv.updateRecord(timestamp, value, searchResult.index());
+                        segment.put(key, sv.serialize());
+                    } else {
+                        if (writeToOlderSegmentNeeded) {
+                            // existing record needs to be moved to an older segment.
+                            // it's important that this step happens before updating the current
+                            // segment. if there is a partial failure (this step succeeds but the
+                            // update to the current segment fails), updating the older segment
+                            // first means there will not be data loss. (rather, there will be
+                            // duplicated data which is fine as it can/will be reconciled later.)
+                            final T olderSegment = versionedStoreClient
+                                .getOrCreateSegmentIfLive(segmentIdForTimestamp, context, observedStreamTime);
+                            if (olderSegment != null) {

Review Comment:
   nit: add comment about `olderSegment == null` case



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