at-least-once

RU: at-least-once

A message-delivery guarantee that ensures every message is delivered to the consumer at least one time, but allows duplicates when a producer retries after a network failure or a consumer crashes before acknowledging. Systems that rely on at-least-once delivery must use idempotent consumers — via deduplication keys, versioned upserts, or naturally idempotent operations — to avoid processing side-effects more than once.