Delivery & reliability
Delivery guarantees
Delivery guarantees describe whether a messaging system may lose, repeat or uniquely process messages within a specified scope and under stated failure conditions.
Also found under: At-most-once, At-least-once, Exactly-once
How it works
At-most-once allows loss without redelivery; at-least-once permits duplicates while retrying delivery. Exactly-once claims need a clear boundary, because a transport cannot by itself ensure a business action happens once. Consumer deduplication, durable storage and transactional processing are separate concerns.
In a Pubb integration
Pubb publication acceptance and idempotency are not promises of exactly-once subscriber processing or offline delivery. Design clients to recover authoritative state and make sensitive business operations idempotent in your backend.
Publish an eventA practical example
A payment event updates a display, but the payment itself is recorded and deduplicated in your database. Repeating the UI event must not initiate another charge.