When Waiter receives an order - he fires a CDI event. On the other hand Barista acts as a listener for ordered coffees (@CoffeeOrdered and @Observes). As a result Barista and Waiter are loosely coupled and moreover they don't know anything about each other.
Cache based Coffee Events
Beyond good espressos
As you can see - introducing CDI improved the service a lot. Now Waiter does not hurry Barista with the orders. This is why they serve the best espresso in the world there...
They have also a lot more time to think about other improvements (and to be honest... I think they will introduce CacheEntryModifiedEvent, CacheEntryRemovedEvent and CacheStartedEvent really shortly)... Or perhaps they'll find some other ideas in Infinispan's manual?