When should Azure Service Bus be used with Dynamics 365?

Service Bus is a message queue. It solves two problems that direct integration handles poorly.

The recipient is not always available

With direct calls, the transfer fails when the receiving system is down or slow, and someone has to clean up. With a queue, the message is placed there and processed when the recipient is ready. This is the main reason for introducing it.

Multiple recipients need the same event

If both the financial system and a notification system need to know that an order has been created, they can both listen to the same queue. Without this, Dynamics 365 must know about each recipient, and every new recipient requires a change to the CRM.

When it is unnecessary

A single integration with one stable system and moderate volume. In that case, Service Bus adds another component that needs to be operated and monitored without solving a problem you actually have.

Consider the operating cost

A queue needs to be monitored. Messages that fail repeatedly end up in a separate queue, and someone needs to review them. If no one is responsible for that monitoring, the queue becomes a place where errors quietly disappear.