public interface StreamPartitioner<K, V> {

    @Deprecated(since = "4.3", forRemoval = true)
    Optional<Set<Integer>> partitions(String topic, K key, V value, int numPartitions);

    /**
     * Determine the number(s) of the partition(s) to which a record with the given key and value should be sent,
     * for the given topic and current partition count
     * @param topic the topic name this record is sent to
     * @param key the key of the record
     * @param value the value of the record
     * @param headers the record headers
     * @param numPartitions the total number of partitions
     * @return an Optional of Set of integers between 0 and {@code numPartitions-1},
     * Empty optional means using default partitioner
     * Optional of an empty set means the record won't be sent to any partitions i.e drop it.
     * Optional of Set of integers means the partitions to which the record should be sent to.
     * */
    default Optional<Set<Integer>> partitions(String topic, K key, V value, Headers headers, int numPartitions) {
        return partitions(topic, key, value, numPartitions);
    }
}

    // already existing method
	@Deprecated(since = "4.3", forRemoval = true)
    public <K> KeyQueryMetadata queryMetadataForKey(final String storeName,
                                                    final K key,
                                                    final Serializer<K> keySerializer) {
        return queryMetadataForKey(storeName, key, new RecordHeaders(), keySerializer);
    }

    // already existing method 
	@Deprecated(since = "4.3", forRemoval = true)
    public <K> KeyQueryMetadata queryMetadataForKey(final String storeName,
                                                    final K key,
                                                    final StreamPartitioner<? super K, ?> partitioner) {
        return queryMetadataForKey(storeName, key, new RecordHeaders(), partitioner);
    }

    /**
     * Finds the metadata containing the active hosts and standby hosts where the key being queried would reside.
     *
     * @param storeName     the {@code storeName} to find metadata for
     * @param key           the key to find metadata for
     * @param headers       the record headers
     * @param keySerializer serializer for the key
     * @param <K>           key type
     * Returns {@link KeyQueryMetadata} containing all metadata about hosting the given key for the given store,
     * or {@code null} if no matching metadata could be found.
     */
    public <K> KeyQueryMetadata queryMetadataForKey(final String storeName,
                                                    final K key,
                                                    final Headers headers,
                                                    final Serializer<K> keySerializer) {
        validateIsRunningOrRebalancing();
        return streamsMetadataState.keyQueryMetadataForKey(storeName, key, headers, keySerializer);
    }

    /**
     * Finds the metadata containing the active hosts and standby hosts where the key being queried would reside.
     *
     * @param storeName     the {@code storeName} to find metadata for
     * @param key           the key to find metadata for
	 * @param headers       the record headers
     * @param partitioner   the partitioner to be used to locate the host for the key
     * @param <K>           key type
     * Returns {@link KeyQueryMetadata} containing all metadata about hosting the given key for the given store, using
     * the supplied partitioner, or {@code null} if no matching metadata could be found.
     */
    public <K> KeyQueryMetadata queryMetadataForKey(final String storeName,
                                                    final K key,
												    final Headers headers,
                                                    final StreamPartitioner<? super K, ?> partitioner) {
        validateIsRunningOrRebalancing();
        return streamsMetadataState.keyQueryMetadataForKey(storeName, key, headers, partitioner);
    }