Message queues are one of those architectural choices where the wrong pick haunts you for years. Pick Kafka when RabbitMQ would have done, and you've bought a 3-node cluster, ZooKeeper (or KRaft) operations, partition management, and consumer group coordination — all to replace what would have been a single RabbitMQ box. Pick RabbitMQ when Kafka was the right call, and you'll spend months migrating when throughput overwhelms you. At Xenotix Labs we've shipped systems using both. This post is a concrete decision guide, with two case studies from our own work. The one-sentence summary RabbitMQ is a message broker. Kafka is a distributed event log. They look similar on the surface, but their internal models are completely different — and that shows up in how you use them. RabbitMQ model: work queues RabbitMQ is optimized for task distribution. A producer sends a message, the broker routes it to one of many competing consumers, the consumer acks, and the message is deleted from the queue.…