Queues & Jobs labs
Anything that runs 'later' or 'elsewhere' — a webhook, a cron job, a queued task — has to cope with retries, duplicates, crashes and overload. These labs let you break each one on purpose and see which pattern (fast ack, idempotency, backoff, locks, dead-letter queues) saves you.
4 free interactive labs — Webhooks: Delivery, Retries & Signatures, Cron Jobs: Schedules, Overlaps & Missed Runs, Job Queues with BullMQ (Redis), RabbitMQ: Exchanges, Queues, Acks & Dead Letters. Each one has an easy-to-hard set of examples, a written explanation and a FAQ, and runs entirely in your browser.
Why you get duplicate deliveries, lost events and forged requests — and how to stop them.
Write a cron expression and watch what really happens when jobs overlap or the scheduler is down.
Watch jobs move through waiting, active, delayed, completed and failed — and see what BullMQ stores in Redis.
Direct, topic and fanout routing, competing consumers, prefetch, redelivery and dead-letter queues, drawn.