If I wanted to learn more back end I would just learn more about PostgreSQL features. It seems like a solid long term investment. You can bet on it even if the Rails vs. Node vs… thing is uncertain.<p>There is a lot of innovation running atop of it too: Suprabase and things like that for example (which are more funky things that can be learnt as needed)
Distributed Systems lecture series by Martin Klepmann - <a href="https://www.youtube.com/watch?v=UEAMfLPZZhE&list=PLeKd45zvjcDFUEv_ohr_HdUFe97RItdiB" rel="nofollow">https://www.youtube.com/watch?v=UEAMfLPZZhE&list=PLeKd45zvjc...</a>