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What are the different delivery semantics in Kafka (at least-once, at-most-once, exactly-once)?

Spark/Big Dataeasy0.5 min readPremium
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Fragma Data Systems
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97 wordsInterview-ready
**At-most-once**: Producer fires and forgets. Messages may be lost. Use for metrics where loss is acceptable. **At-least-once**: Producer retries until ack; consumer may see duplicates. Simpler; use with idempotent consumer. **Exactly-once**: Transactional producer + transactional consumer (Kafka 0.11+). Producer commits atomically; consumer reads-processes-commits in transaction. No duplicates, no loss. **Why It Matters**: Financial transactions, billing, inventory need exactly-once....
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