Backend · Mid-level · Theory

A queue consumer processes "award bonus points" messages, and sometimes users get their bonus twice. Why does this happen, and how do you fix it?

~4 min by voice

How to approach it

They're checking whether you understand at-least-once delivery semantics and can design an idempotent consumer, rather than hunting for a "producer bug" or hoping for exactly-once in the broker.

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message queues idempotency

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Answer by voice

The interviewer will ask this question and listen. Think out loud and ask for a hint if you need one. When you're done, pause or tap “That's my answer”. In about a minute, your score and the points you covered show up here.

Best with headphones · ~4 min