If you don’t know Moodle, it is the most popular learning platform around the world and it is used by many Universities around the world. All Moodle is done in PHP, however, for a new project, MoodleNet an open and federated social network to share learning resources, they have chosen Elixir. In fact, I have been hired to do it and I’m the only developer that actually knows the technology.
We wrote a small blog post about it: https://blog.moodle.net/2018/elixir-choice/
But also there is a more detailed explanation about this here: https://docs.moodle.org/dev/MoodleNet/tech/stack
I think it could be very useful for the community how external developers and (big) companies see our technologies and what they expect about it. I’ll be happy to answer any questions you have.