Ahh, thanks Jacek for catching my omission. I only looked at the first "pair" and they were tied by date so I assumed the rest were as well.

I also do not understand why the middle tier would care what order they are returned in. I mean how can you guarantee that Orderer 4 will always place orders before Orderer 8? In theory, Orderer 8 could be a more efficient worker and enter 4 orders in 5 minutes while Orderer 4 does 2. Then the order may be

8 10:15:10

4 10:15:11

8 10:16:29

4 10:17:01

8 10:18:01

8 10:19:30