Queuing of messages

[robmir44]

Hello, I have one question, maybe I misunderstood the messaging-bus concept.
I'm using microservice architecture (stateless) with REST APIs. E.g. when an API is called then during the processing I want to access a bus-system and i want to get newest data for a certain topic. it's just possible when the message on the queue keeps as long as new message will be published. It means the message can not be deleted, only publishing of new data on the topic can rewrite the data => similar to redis (hashmap).

The problem in microservice architecture is that callback functions are useless, because as i said this is stateless architecture. What would be the solution by using nats? Thanks!