Queues & Async Processing
Take the slow work out of the request, promise to do it soon, and smooth every spike.
5 lessons · ~50 min · free
By the end you can
- Move slow work off the request path with a queue and workers
- Explain at-least-once delivery, acks, retries, and dead-letter queues
- Read queue depth as a signal and scale consumers to it
- Make handlers idempotent so duplicate delivery stops mattering
- Choose between a queue, pub/sub, and a log/stream on purpose
Lessons
Start the course- The slow thing in the fast path9 minA 3-second job inside a 200ms request, and the queue that takes it off the clock.
- The life of a message11 minAcks, visibility timeouts, retries, and the dead-letter queue where poison messages go.
- Queue depth is a gauge10 minBursty producers, steady consumers, and scaling workers off the number that matters.
- Delivered twice, applied once11 minWhy duplicates are normal, idempotency keys, and effectively-once as a system property.
- Queue, pub/sub, or stream9 minOne consumer, fanout, or replayable history: picking the shape, plus when async is wrong.
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Design with it after
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