I've been tinkering with my own little project from scratch over here: https://github.com/nickyvanurk/3d-multiplayer-browser-shooter but how do I take it to the next level and do this kind of work as a job?

Are there learning resources or is everything learned on the job?

I feel the MMO netcode community, and netcode community in general, is very small. So I can't find much books on the subject. I was hoping for a little guidance.

I really enjoy netcode, optimizing, game engine architecture, entity-component-systems, scalability (how to go from 100 to 10 mil users? this get's me so excited). So I thought MMO network programmer would be the perfect job for me. Is this a safe assumption? (I also love MMO games the most).

I already learned the netcode stuff that's available from the most linked resources (gafferongames, gabriel, etc... usually it's all focused on FPS games tho).