> I think the same argument can be made with "only one Kafka cluster"
No it can't. Kafka events for the same partition will always be processed in order. If you have a stream transformation that reads from a topic that lives in one cluster and writes to a topic that lives in another cluster, then (as long as you chose the right partition key) everything will work correctly. Even if you have a sequence of transformations that zig-zag between two different clusters, it will do the right thing. You can't achieve that with traditional databases.
No it can't. Kafka events for the same partition will always be processed in order. If you have a stream transformation that reads from a topic that lives in one cluster and writes to a topic that lives in another cluster, then (as long as you chose the right partition key) everything will work correctly. Even if you have a sequence of transformations that zig-zag between two different clusters, it will do the right thing. You can't achieve that with traditional databases.