Elixir is great and modern programming language. But, according to the Sonny Scroggin, Phoenix Core Team member, Elixir is not a super fast. And even the "raw" CPU doesn't really matter for the majoraty of applications, but there are still couple of reasons that can make you to get the tools that give you access to native power.
In this talk Sonny discusses Native Implemented Functions (NIFs) - Erlang’s Foreign Function Interface (FFI).
NIFs are normally implemented in C and are considered dangerous. But Sonny explores writing safer NIFs in Rust - a new systems programming language developed by Mozilla, that focuses on memory safety. He also touches on the pitfalls with writing NIFs and how Rust can make this process easier and safer.