class CompositeReadOnlyWindowStore implements ReadOnlyWindowStore<K, V> {

    @Override
    public WindowStoreIterator<V> backwardFetch(final K key,
                                                final Instant timeFrom,
                                                final Instant timeTo) throws IllegalArgumentException {
        Objects.requireNonNull(key, "key can't be null");
        final List<ReadOnlyWindowStore<K, V>> stores = provider.stores(storeName, windowStoreType);
        for (final ReadOnlyWindowStore<K, V> windowStore : stores) {
            try {
                final WindowStoreIterator<V> result = windowStore.backwardFetch(key, timeFrom, timeTo);
                if (!result.hasNext()) {
                    result.close();
                } else {
                    return result;
                }
            } catch (final InvalidStateStoreException e) {
                throw new InvalidStateStoreException(
                    "State store is not available anymore and may have been migrated to another instance; " +
                        "please re-discover its location from the state metadata.");
            }
        }
        return KeyValueIterators.emptyWindowStoreIterator();
    }

    public  CompositeReadOnlyWindowStore(final StateStoreProvider provider,
                                        final QueryableStoreType<ReadOnlyWindowStore<K, V>> windowStoreType,
                                        final String storeName);

}