Elixir is pretty fast, but far from the fastest or efficient. IMO if all you need is CRUD server that operates efficiently then elixir is probably the wrong choice unless you already know it. It does have some nice features within distribution and real-time stuff, but if you don't need that and don't know erlang or elixir I wouldn't use it.
But what about not so computation-heavy tasks like parsing HTTP requests, interacting with databases, generating and serving responses based on the input, templates, reasonably simple logic and the data? And if it's not fast then why even consider it when there are more well-established alternatives like Ruby for those who like the syntax, ASP.Net/Core, Python/Django, Node/Express, Scala/Play for the FP lovers etc? I've been previously told it's key features are it's super fast, functional and Ruby-like.
Super fast, no. At least not in the C++ way. Faster than Ruby or Python, yes.
Functional, yes.
Ruby-like, yes, as German is English like (mostly guessable vocabulary.) Then you discover that the two languages work in totally different ways and your Ruby skills don't really matter anything when working in Elixir.