@Override
  public boolean removeMasterKey(int keySeq) {
    LOG.trace("removeMasterKey: keySeq = {}", keySeq);
    return masterKeys.remove(keySeq) != null;
  }
Default in-memory token store implementation.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/security/MemoryTokenStore.java