Node.js · Senior · Question 38 of 75

A message queue delivers messages 'at least once'. What must consumers do?

✓Correct answer: Be idempotent, for example by tracking processed message IDs, because the same message can arrive twice
2Nothing, duplicates are impossible
3Delete the queue after each message

Explanation

Exactly-once delivery is very hard in distributed systems. Idempotent handling makes duplicates harmless.

Further reading

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