@Override
        public synchronized boolean hasNext() {
            if (!open) {
                throw new InvalidStateStoreException(String.format("RocksDB iterator for store %s has closed", storeName));
            }
            return super.hasNext();
        }
A persistent key-(value-timestamp) store based on RocksDB.
streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBTimestampedStore.java