An interesting read by an interesting engineer. Bookmark his site and devour at your own pace.

Highly recommended.

First, multiple baristas may be processing orders using different equipment. Blended drinks may take longer than a drip coffee.

Client side caching and processing is also at play. The cashiers usually fill the drip coffee themselves.

He seems to reject news feeds, any rationale for that? (Can't find a news feed).

It's at the bottom:

http://www.eaipatterns.com/ramblings.rss

I think this is a slightly more detailed version:

http://www.enterpriseintegrationpatterns.com/docs/IEEE_Softw...

Is it Asynchronous communication?