You don’t want stream replication for scale, you want it for availability and durability. The number of times replication has saved my ass is too damn high.

And you want Kafka (or something like it) the moment you need two processes handling updates which again you probably want for availability reasons so a crash doesn’t stop the stream.

You also don’t catch deletes or updates with this setup. But there’s a million db to Kafka connectors that read the binlog or pretend to be a replica to handle this.