Glossary term
What is DLQ (Dead-Letter Queue)?
DLQ stands for Dead-Letter Queue.
In System Design
Where messages go after failing too many times. Example: Malformed messages parked for engineers to inspect.
Learn it properly · System DesignLesson 38: Background Jobs, Retries & Dead-Letter QueuesBackground jobs are easy to start and surprisingly easy to get wrong: poison jobs, retry storms, cron that runs twice, deploys that kill half-done work. How to design jobs, retry only what can succeed, and route what can't to a dead-letter queue you actually watch.In Practical Design Problems
A side queue for messages that keep failing. They stop blocking the main queue, and you can look at them and replay them.
Learn it properly · Practical Design ProblemsLesson 5: Design a Notification System (In-App, Push, Email)Polling, long polling, server-sent events and WebSockets, fan-out with queues, read state, user settings, retries and removing duplicates.