hard20 pts · first answer countskafkareliability

Exactly-once end to end

A consumer reads from Kafka and writes to a database. It commits offsets after writing. If it crashes after the write but before the commit, what happens, and what makes the result correct?

A.Messages are lost; switch to committing before writingB.Kafka automatically rolls back the database writeC.Nothing happens, because Kafka guarantees exactly-once to any external system by defaultD.Messages are reprocessed (at-least-once); make writes idempotent, for example upserts on a unique event ID

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