Dead Letter Queue
ELI5 — The Vibe Check
A dead letter queue is where failed messages go to die (or at least wait for someone to fix them). If a message fails processing after multiple retries, instead of losing it or retrying forever, it goes to the DLQ. It's the 'return to sender' pile of message queues.
Real Talk
A dead letter queue (DLQ) is a secondary queue that stores messages that couldn't be processed successfully after exhausting retry attempts. It prevents poison messages from blocking the main queue while preserving them for debugging, manual intervention, or reprocessing. DLQs are standard in AWS SQS, RabbitMQ, Kafka, and most message brokers.
When You'll Hear This
"Check the dead letter queue — there are 200 failed payment messages from last night." / "We replay DLQ messages after fixing the bug that caused the failures."
Related Terms
Job Queue
A job queue is a to-do list for your server.
Message Queue
A Message Queue is a waiting room for tasks. Producers drop tasks in the queue, consumers pick them up and process them one at a time.
Poison Message
A poison message is a message that crashes your consumer every time it tries to process it.
Retry Pattern
Retry Pattern is trying something again when it fails, because sometimes failures are temporary (network hiccup, brief overload).