@Override
    public void doPrefetch(int index, long relativeOffset, long size) {
      ByteBuffer bufferToWrite = buffers.get(index);
      bufferToWrite.position((int) relativeOffset);
      bufferToWrite.limit((int) Math.min(size + relativeOffset, bufferToWrite.capacity()));
      buffers.set(index, bufferToWrite);
    }
A mock implementation of {@link Store} that store all details in memory.
ambry-replication/src/test/java/com/github/ambry/replication/InMemoryStore.java