How does Kafka guarantee message ordering with multiple producers?

Kafka only guarantees ordering within a single partition per producer. With multiple producers writing to the same partition, messages are interleaved in arrival order at the leader — there's no coordination between producers. If you need causal ordering across producers (message A must be seen before B), use a single producer with sequential sends, or include timestamps/sequence numbers in message payloads and sort at the consumer. Kafka transactions can ensure atomic multi-partition writes but don't impose cross-producer ordering.

Expected key concepts: single partition, interleaved, arrival order, causal ordering, single producer, sequential, timestamps, sequence numbers, sort, transactions