> turn to Redis Cluster Streams instead. So much simpler to manage and so much cheaper to run

I don't have any experience with Redis Cluster Streams. Could you please tell us how it is simpler to manage? IMO, installing and managing a Kafka cluster in a non Fortune 100 scale is simple enough: run 1 java command for zookeeper, run another java command for a broker (with recent version of Kafka, zookeeper is not needed anymore). The configuration files are not very simple but not very complicated either. When we have another machine, we can run another broker on it.

Redis Cluster Streams is cheaper to run because it's written in C, doesn't need a VN to run? Or because its messages are stored in RAM not SSD?

I haven’t used Kafka since the change to remove zookeeper, it’s likely they’re more or less on par now. Redis gets a win because most shops already have Redis, it’s already trusted and installed, just waiting for its first XADD.