At-least-once delivery.
also: at-least-once · at least onceMessages are retried until acknowledged, so none are lost, but some may arrive more than once.
the two-minute refresher
- The sender waits for an ACK and retries if none comes.
- If the message arrived but the ACK was lost, the retry is a duplicate.
- The industry default (webhooks, queues): pair it with idempotent consumers.