Experiment with abstracting the shit out of RabbitMQ to solve any business logic problem. I'm in a different CS field than web development but whenever I've had to implement something business related it almost always was just highly abstract message brokering with React hacked together UI. I learned UI from reading lecture notes on 'Human Computer Interface' design from the plenty of university courses around offering this subject http://www.cs.cmu.edu/~bam/uicourse/05863fall17/schedule.htm...
For learning web app APIs all I did was search Google Scholar for 'API design' and read whatever was available. Joshua Bloch has a good paper on API design. As for scaling, containers, concurrency ect look at Elixir w/Phoenix framework instead, or Erlang w/Yaws and just run it on a cheap FreeBSD comanaged box or deploy Phoenix to Heroku. BEAM will take care of the scaling. There's books around https://pragprog.com/book/lhelph/functional-web-development-...
For learning web app APIs all I did was search Google Scholar for 'API design' and read whatever was available. Joshua Bloch has a good paper on API design. As for scaling, containers, concurrency ect look at Elixir w/Phoenix framework instead, or Erlang w/Yaws and just run it on a cheap FreeBSD comanaged box or deploy Phoenix to Heroku. BEAM will take care of the scaling. There's books around https://pragprog.com/book/lhelph/functional-web-development-...