I have new question followed, eg: I have item1, item2, item3, serverA and serverB process super fast, but when they go through from server A to server B they have waiting time 3 min, 5 min, 1 min. For server B, I want to process the item who arrives first... But now it seems, item2 and item3 have to wait until item1 is done traveling which is not what I want. Because ideally we want to make improve the utilization of both servers.