I have been mentoring Elixir on Exercim.io for over a year now.
In that time I have mentored 4903 solutions across Elixir and Groovy.
This is a great way to keep your skills upto date in a language.
The students will challenge you with details that you will need to research. It’s the questions that you get that will stretch your knowledge.
You will need to explain unusual bugs and concepts to people who may not have english as their first language.
Developer Rants 