public Object remove() throws ForceReattemptException {
    Object key = eventSeqNumDeque.removeFirst();
    if (key != null) {
      destroyKey(key);
    }
    return key;
  }
It removes the first key from the queue.

@return Returns the key for which value was destroyed.
geode-core/src/main/java/org/apache/geode/internal/cache/BucketRegionQueue.java