Glossary term
What is Outbox pattern (transactional outbox)?
Outbox pattern stands for transactional outbox.
In System Design
Save data + "event to publish" in one DB transaction. Example: Solves "DB updated but event not sent".
Learn it properly · System DesignLesson 37: At-Most-Once, At-Least-Once, Exactly-OnceAcknowledge too early and a crash loses the payment; acknowledge too late and it charges twice. At-most-once, at-least-once and why true exactly-once is impossible — plus idempotent consumers, Kafka's exactly-once and the transactional outbox.In Full-Stack Questions
Saving a message in the same database transaction as your data, then sending it from there later, so nothing is lost.
Learn it properly · Full-Stack QuestionsLesson 19: Queues, Background Jobs and WebhooksWhy queues, BullMQ, retries and backoff, dead letters, idempotency, the outbox pattern, receiving and sending webhooks, RabbitMQ vs Kafka vs SQS.