The telecom industry knows what high availability means. Millions of calls have to be routed in parallel without the service going offline. More than 30 years ago a programming language called Erlang was developed for exactly this.
Nowadays there are more and more platforms in the web that have similar tough requirements. This is why Elixir was created: the modern programming language for the Erlang ecosystem.
Fun fact: the Renuo website was written in Elixir.