TLDR: The problem domain (telecom) fits Elixir perfectly

If you’re talking about scaling this, Elixir is built on the BEAM VM which was originally made for Ericsson and is tailor made for telecom systems.

Its whole paradigm is built around the concept of Let It Fail, which is basically about achieving fault tolerance through isolation and supervision.

So aside from the fact that Elixir+Phoenix is a productive framework that allowed the author to build this in a few days, it also means that it will scale very well with minimal code changes.

For reference, one of the solutions you might use to distribute this in Python is Celery, which is built on RabbitMQ which is built on Erlang, which is the predecessor of Elixir.