> Services relying on Pub/Sub should be idempotent anyway. If you need to work around that for some reason, you are better off dumping messages from your subscriber into RabbotMQ or Redis for processing and use a Subscriber/Scheduler/Worker pattern.

Exactly. Pub/Sub is made to send messages to any consumer. To bring in order you direct messages to a specific consumer. Alright well Pub/Sub wasn't the right tool then.