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Two events about the same order arrived at my consumer out of order, and I don't know why since I published them one after another.
What you'll have at the end
A Kafka producer keyed by the order's own identifier, with a test proving every event for one order arrives in order
You need
A producer that already publishes more than one event about the same real-world record, such as an order or account, into a Kafka topic with more than one partition, plus a consumer group you can run with more than one instance.
Not covered
Recovering the guarantee after a topic's partition count changes isn't covered here: that shifts which partition every key lands on and needs its own migration plan once real history exists.
Leans on
Should this event stream run on RabbitMQ or Kafka?
if you haven't settled which platform this stream runs on yet, that choice comes first; this recipe assumes it's already made.
Prove a message reached the broker with a publisher confirm
covers whether the broker even received the event at all, a separate guarantee from the ordering this recipe fixes.
Checked 19 Aug 2026
Part of the Message Queues cookbook