I see your point, but I still don't think you can just say "If you want to get a job as a Go developer, you must know gRPC." Even more so for Kafka, I've only heard about it being popular in the Java world. You can't even say "If you want to get a job as a Java developer, you must know Spring." Nowadays, sane Java projects use https://vertx.io, it's just too good. I would argue that Spring is for legacy projects only.