Interview questions
Idempotency, retries & failure handlingHardSDE-3

A Flink job counts ad clicks per campaign per minute and writes the counts to a database for billing. After a job restart, some campaigns were billed twice for the same minute. How do you make this pipeline correct?

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Answer out loud as you would in the room — clarify, give numbers, name the trade-off — then compare with the model answer.

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