- Erlang/Elixir: taught me functional programming, pattern matching, recursion, supervision, how to achieve fault tolerance - Docker: taught me about server ma

- Erlang/Elixir: taught me functional programming, pattern matching, recursion, supervision, how to achieve fault tolerance - Docker: taught me about server management and immutable infrastructure; paved the way for a lot of concepts (containers are surprisingly foreign for a lot of people) Other than that: learning about different databases in general and learning how they solved the problems they had and why they solved them that way; the same problems come up over and over and it's important to be able to recognize good ideas from bad ones as well as when to recognize solved problems from novel ones