Recode Hive
How do you choose between at-least-once and exactly-once message processing? #996
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When designing a message-driven or event-based system, choosing the delivery semantics can significantly impact complexity and correctness. In practice, how do you decide between at-least-once and exactly-once processing? |
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In most real systems, the decision is less about guarantees and more about cost. I default to at-least-once processing combined with idempotent consumers. It provides strong reliability while keeping operational complexity manageable. Exactly-once processing becomes justified only when: Side effects are irreversible or extremely expensive to roll back. Idempotency is impractical or impossible. The system already depends on transactional guarantees across boundaries. In many cases, exactly-once semantics shift complexity from the consumer to the infrastructure, often making failure modes harder to reason about. For that reason, I treat it as an optimization for specific constraints rather than a default design choice. |
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In most real systems, the decision is less about guarantees and more about cost.
I default to at-least-once processing combined with idempotent consumers. It provides strong reliability while keeping operational complexity manageable.
Exactly-once processing becomes justified only when:
Side effects are irreversible or extremely expensive to roll back.
Idempotency is impractical or impossible.
The system already depends on transactional guarantees across boundaries.
In many cases, exactly-once semantics shift complexity from the consumer to the infrastructure, often making failure modes harder to reason about. For that reason, I treat it as an optimization for specific constraints rather …