@Override
  public MessageInfo findKey(StoreKey key) throws StoreException {
    MessageInfo info = getMergedMessageInfo(key, messageInfos);
    if (info == null) {
      throw new StoreException("Key " + key + " not found in store. Cannot check if it is deleted",
          StoreErrorCodes.IDNotFound);
    }
    return info;
  }
Log that stores all data in memory.
ambry-replication/src/test/java/com/github/ambry/replication/InMemoryStore.java