/*
 * 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.query;

/**
 * Marker interface that all interactive queries must implement (see {@link
 * org.apache.kafka.streams.KafkaStreams#query(StateQueryRequest)}).
 * <p>
 * You can find all available queries by searching for classes implementing this interface.
 * <p>
 * Kafka Streams will pass unknown query types straight through into the bytes stores, so callers
 * can add custom queries by implementing this interface and providing custom stores that handle
 * them (via {@link org.apache.kafka.streams.state.StoreSupplier}s.
 * <p>
 * See KIP-796 (https://cwiki.apache.org/confluence/x/34xnCw) for more details.
 *
 * @param <R> The type of the result returned by this query.
 */
public interface Query<R> {

}
