Dead-letter queue
Also called: DLQ
A separate queue where messages that keep failing are moved, so they stop blocking the rest and can be inspected later.
Definition
After a message fails a set number of times (malformed data, a bug, a permanently missing record), the consumer or broker moves it to a dead-letter queue instead of retrying forever. Someone must be alerted and fix or replay those messages; a dead-letter queue nobody watches silently loses work.
In practice
An OrderPlaced event with an invalid currency goes to orders-dlq after 5 attempts, and an alert fires.
Learn it in context
Lessons that use this term.