Consumer Groups and Offsets

Concepts: paEventPlatforms

What They Want to Hear 'Each consumer in a group tracks its position in the partition using offsets. After processing a batch of events, the consumer commits its offset. If the consumer crashes, it restarts from the last committed offset. This gives at-least-once delivery by default. For exactly-once, I use the transactional pattern: commit the offset and write the output in the same transaction, so either both happen or neither does.' This is the answer that shows you understand the offset commit lifecycle and why exactly-once requires transactional writes.