---
title: "Set aside messages that keep failing · Agent Wranglers"
url: https://agentwranglers.se/playbook/scaling/background-jobs-and-queues/dead-letter-queue
updated: 2026-10-21
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Set aside messages that keep failing

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Background jobs and queues](https://agentwranglers.se/playbook/scaling/background-jobs-and-queues.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers). Updated 2026-10-21.

- ID: SCL-34
- Level: Recommended
- Chapter: [Background jobs and queues](https://agentwranglers.se/playbook/scaling/background-jobs-and-queues)
- Rule: After a set number of failed attempts, move a message or job to a separate dead letter queue and alert. Never retry it forever or drop it.
- How: Count attempts on each message, and back off between them, such as 5 attempts over an hour. After the limit, store the message with its last error, so a person can fix the cause and replay it. Most queues have this built in, such as a redrive policy or a failed jobs table.
- Check: Send a message that always fails. After the limit it sits in the dead letter queue with its error, an alert has fired, and other messages still flow.

## Related rules

- [Retry with backoff and jitter](https://agentwranglers.se/playbook/api-design/reliability/retry-backoff) in API design
- [Decide what happens when a provider is down](https://agentwranglers.se/playbook/api-design/using-other-companies-apis/provider-outages) in API design
- [Validate every event before you store it](https://agentwranglers.se/playbook/data/product-analytics/event-validation) in Data
- [Alert on the age of the oldest waiting job](https://agentwranglers.se/playbook/operations/alerts-and-on-call/queue-age) in Operations
- [Use BullMQ or RQ for background jobs](https://agentwranglers.se/playbook/stack/databases-and-storage/background-jobs) in Software choices
- [Give every job a time limit](https://agentwranglers.se/playbook/scaling/background-jobs-and-queues/job-time-limits) in Scaling

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/scaling/background-jobs-and-queues/dead-letter-queue">Agent Wranglers scaling playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Spread scheduled work across the hour](https://agentwranglers.se/playbook/scaling/background-jobs-and-queues/spread-scheduled-jobs)
- Next: [Run each scheduled job once at a time](https://agentwranglers.se/playbook/scaling/background-jobs-and-queues/single-job-runs)
- [Background jobs and queues](https://agentwranglers.se/playbook/scaling/background-jobs-and-queues)