Operations and quality assurance
Dead letter queue
In short and in plain language
The dead letter queue holds operations that still failed after several attempts.
One example is an order with a product number the target system does not know.
They stay there with the error message. So they do not get lost silently. Once the cause is fixed, they can be sent again.
Definition
Operations that could not be processed even after several attempts end up in the dead letter queue — an order with a product number unknown to the target system, for instance. They stay there together with the error message instead of disappearing silently, and can be replayed once the cause is fixed.