I never used the amazon services karma uses (SQS and SNS) to wire thing up, but I believe that is a really good read:
https://blog.yourkarma.com/building-microservices-at-karmaOn our side we are all http on the request-response services, however with
iron.io releasing their solution for on premise I strongly believe that a setup could have the front end apps hit the http backend end-points directly and if not available then queue them up on the nifty
iron.io http rest queues.
Cheers!
-Simo