{"head":{"title":"What Is a Message Queue? Definition and Example | OceanLab","description":"A message queue holds tasks or events until a worker is ready for them, so the main app does not wait. How queues work, an example and common mistakes.","canonical":"https://oceanlab.in/glossary/message-queue"},"crumbs":[{"name":"Home","path":"/"},{"name":"Glossary","path":"/glossary"},{"name":"message queue","path":"/glossary/message-queue"}],"slug":"message-queue","term":"Message queue","aka":["job queue","task queue"],"category":"System design","short":"A buffer that holds messages, such as tasks or events, until a worker is ready to process them, so the sender does not have to wait.","body":[["A producer puts a message on the queue, for example send this email or resize this image. One or more workers take messages off, do the work and confirm. If a worker fails, the message goes back on the queue or to a dead letter queue for review."],["Queues are the plumbing behind ",{"href":"/glossary/event-driven-architecture","text":"event-driven architecture"},", background jobs and smoothing spikes: the queue grows during a rush and drains afterwards."]],"why":["Slow or unreliable work, such as calling third-party APIs, generating reports or running AI tasks, should not make users wait or fail their request. A queue moves it to the background and retries it safely, and workers can scale on queue length."],"example":["An AI document tool lets users upload hundreds of contracts at once. Each upload adds a job to a queue. Workers pick up jobs, call the model and save results, and the user sees progress as each one finishes, without the app timing out."],"inBuild":["We use a managed queue, make every worker ",{"href":"/glossary/idempotency","text":"idempotent"}," because messages can be delivered more than once, set retry limits with backoff, send poison messages to a dead letter queue and alert on queue age, not just length."],"mistakes":[["Assuming each message is delivered exactly once."],["Retrying forever, so one bad message blocks the queue."],["No alert when the queue backs up, so users wait hours before anyone notices."]],"related":[{"href":"/glossary/event-driven-architecture","label":"Event-driven architecture","detail":"A way of designing software where parts of the system publish events about what happened, and other parts react to them on their own."},{"href":"/glossary/idempotency","label":"Idempotency","detail":"The property of an operation that has the same effect whether it runs once or several times, so it is safe to retry."},{"href":"/glossary/webhook","label":"Webhook","detail":"An HTTP request one system sends to a URL you choose as soon as an event happens, so you do not have to keep asking."},{"href":"/glossary/autoscaling","label":"Autoscaling","detail":"Automatically adding or removing computing capacity, such as servers or containers, as the load on a system goes up or down."},{"href":"/glossary/rate-limiting","label":"Rate limiting","detail":"Capping how many requests a user, API key or address can make in a given time, to protect a system and share capacity fairly."}],"tools":[{"href":"/tools/workflow-automation-roi","label":"Workflow automation ROI","detail":"Free tool"}],"links":[{"href":"/ai-automation","label":"AI automation","detail":"How OceanLab automates company workflows with AI."}],"sources":[],"legal":false,"updatedAt":"2026-10-25"}