Work Queues: Retries, Idempotency, and DLQs Explained

This article explains work queue fundamentals: delivery semantics (at-least-once, at-most-once, exactly-once), visibility timeout calculation, idempotent job design with deduplication keys, and retry strategies with exponential backoff and dead-letter queues. It covers choosing between SQS, RabbitMQ, Redis/BullMQ, and Kafka based on volume and use case. The outbox pattern is introduced to prevent dual-write problems between databases and queues.