Dead-Letter Queue
A queue used to isolate messages that cannot be processed successfully in the normal consumption path, avoiding endless retries while preserving the failed record for inspection or later handling.
If a message triggers the same deterministic failure on every attempt, returning it to the main queue can block useful progress. A dead-letter queue removes that record from the normal path while keeping it available for diagnosis or controlled replay.
A DLQ does not fix the underlying failure. Before replay, idempotency, schema compatibility, and the original fault need to be checked. That makes it part of the same failure boundary as safe retry design.