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Delivery Semantics

Message delivery semantics define the guarantees a messaging system provides regarding the delivery of messages.

Delivery Semantics

At-Most-Once​

Messages are delivered once or not at all. (Fire and forget).

At-Least-Once​

Messages are guaranteed to be delivered, but duplicates may occur.

Exactly-Once​

Messages are delivered exactly once. This is the hardest to achieve and requires coordination between producers, brokers, and consumers.