Message Queues

Design Dead-Letter Queues for Poison Messages

Retries are useful when a failure is temporary. A database may be unavailable for a few seconds, a downstream service may return an overload response, or a network connection may disappear and recover. Retries become harmful when the message itself cannot succeed. A malformed payload, an unsupported schema version, a reference to permanently missing data, or a deterministic application bug can make the same message fail on every delivery. If the broker keeps returning that message to consumers indefinitely, the system spends capacity repeating work that has no chance of succeeding.