@Override
    public Future<Map<ByteBuffer, ByteBuffer>> get(final Collection<ByteBuffer> keys) {
        return executor.submit(() -> {
            Map<ByteBuffer, ByteBuffer> result = new HashMap<>();
            for (ByteBuffer key : keys) {
                result.put(key, data.get(key));
            }
            return result;
        });
    }
Implementation of OffsetBackingStore that doesn't actually persist any data. To ensure this
behaves similarly to a real backing store, operations are executed asynchronously on a
background thread.
connect/runtime/src/main/java/org/apache/kafka/connect/storage/MemoryOffsetBackingStore.java