I want to make clear that I'm not intentionally faulting the OP in this situation, because the decision with regards to message brokers isn't easy in a complex

I want to make clear that I'm not intentionally faulting the OP in this situation, because the decision with regards to message brokers isn't easy in a complex system. Often you have to mix "lossy" messages (pubsub) with simple ack messages (receipt confirmation) as well as full RPC-style messaging (receipt ack, result response) and that is usually a non-trivial endeavor from both an architectural as well as implementation standpoint.