beginnerBuilding the Producer Microservice
Why does the choice of a message key (not just the value) matter when producing to a partitioned topic?
Kafka uses the key's hash to deterministically choose which partition a message lands in, which means all messages with the same key (e.g. the same `orderId`) always go to the same partition and are therefore processed IN ORDER relative to each other. No key means round-robin partitioning with no ordering guarantee across messages about the same entity.
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