public interface ReactiveKeyValueStore<K, V> {

   CompletionStage<V> get(K key);

   CompletionStage<Void> save(K key, V value);

   CompletionStage<Void> remove(K key);

   CompletionStage<Void> putMany(Publisher<Entry<K, V>> pairs);

  Publisher<Entry<K, V>> entries();

  ...

}