Erlang - Because it handles scalability and reliability very well, is Actor based (each process being an Actor), has a great library for backend stuff in OTP, a

Erlang - Because it handles scalability and reliability very well, is Actor based (each process being an Actor), has a great library for backend stuff in OTP, and because I love it. Tie between Elixir (because scripting language that runs on Erlang BEAM), and Javascript (because it is so ubiquitous, despite having so many bad parts - though it has a fair share of good parts too). Java - Because it is the modern COBOL...everyone hates it, but there are so many systems and shops that use Java that it becomes a de factor requirement to learn it. Close runners up are: * Clojure - Because it is based on Scheme, which is based on Lisp, and takes the functional approach. * Python - Because the philosophy and syntax are beautiful * Ruby - Because it is really fast to get web server stuff done