Queues are used to be able to have bursts of requests without overloading the server, which may be less performant than needed to service those bursts of reques

Queues are used to be able to have bursts of requests without overloading the server, which may be less performant than needed to service those bursts of requests directly. With the message bus the clients can (roughly) send requests as frequently as they want, while servers will handle them as fast as they can, without the danger of missing a request or having clients to wait. The queue is the "asynchronization" mechanism.