The asynchronous access pattern follows the fire-and-forget approach to data access. In this case, once the middleware forwards the request, it doesn't wait for the response for that request to arrive back and moves on the handling of the newer requests that it's receiving.

The asynchronous access pattern is usually followed in the mediation approach, where the router middleware, once notified about the occurrence of a certain event, propagates the event forward and forgets about the event without waiting for its reply.

The same is the case with the message bus model; the message bus, once it has delivered a message, does not care about the response for the message being generated, hence making the process an asynchronous process.