Erlang (programming language)

The original that Elixir and Gleam stand on, worth learning for what it teaches about failure. Erlang was built for massively scalable soft real-time systems that must stay available, and its OTP libraries turn "let it crash" from a slogan into a design method: small isolated processes, supervisors that restart them, and message passing instead of shared state. The syntax, a legacy of Erlang's start as a modified Prolog, is terse and a little odd at first, and the tooling feels older than its descendants'. Pick Erlang when you want to understand the BEAM from the ground up or work on an existing Erlang system; pick Elixir or Gleam when you just want to build something on it.