I am working on a project where a website needs to exchange complex and confidential (and thus encrypted) data with other systems. The data includes personal information, technical drawings, public documents etc.
We would prefer to avoid the Request-Reply pattern to the dependent systems (and there are a LOT of them), as that would create an awful lot of empty traffic.
On the other hand, I am not sure that a pure Publisher/Subscriber pattern would be appropriate -- mainly because of the complex and bulky nature of the data to be exchanged.
For that reason we have discussed the possibility of a "publish/subscribe/request" solution. The Publish/Subscribe part would be to publish a message to the dependent systems, that something is ready for pickup. The actual content is then picked up by old-school Request-Reply action.
How does this sound to you?