Backend & systems·Queues, streams and delivery semantics
you make the duplicate delivery harmless by deduplicating on a key or committing the offset in the same transaction as the result.
Exactly-once processing
Also calledexactly once semantics, EOS
The property that each message affects the result exactly once. Exactly-once *delivery* over an unreliable network is impossible; exactly-once *effect* is achievable, by pairing at-least-once delivery with idempotent processing or a transaction spanning the output and the offset commit. When a vendor says exactly-once, this is what they built, and it only holds inside their system boundary.