private void addRemovedEventToMap(Map<Integer, List<Object>> bucketIdToDispatchedKeys,
      int bucketId, Object key) {
    List<Object> dispatchedKeys = bucketIdToDispatchedKeys.get(bucketId);
    if (dispatchedKeys == null) {
      dispatchedKeys = new ArrayList<>();
      bucketIdToDispatchedKeys.put(bucketId, dispatchedKeys);
    }
    dispatchedKeys.add(key);
  }
Take will choose a random BucketRegionQueue which is primary and will take the head element
from it.
geode-core/src/main/java/org/apache/geode/internal/cache/wan/parallel/ParallelGatewaySenderQueue.java