Multi Step Processes hard
Your User Service publishes 'UserCreated' and 'UserUpdated' events. A downstream Consumer sees 'UserUpdated' *before* 'UserCreated', causing a crash. What is the root cause?
- A The queue is broken.
- B The Consumer is multi-threaded.
- C Timestamps are unreliable.
- D The events were sent to different partitions (using Round Robin), and one partition was processed faster than the other.
Answer: D. The events were sent to different partitions (using Round Robin), and one partition was processed faster than the other.
Message queues (Kafka/Kinesis) guarantee order only *within* a partition. To ensure all events for User A arrive in order, they must all go to Partition 1. Sharding by UserID guarantees this.
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