Picking Erlang for number crunching is a Bad Idea™. You can use NIFs in C or Rust though for expensive computations. If you play to its' strengths it outshines the competition eg WhatsApp and 99.999999999% of uptime (that is a few seconds of downtime per year). Horses for courses.

[Edit]

Zero snark intended.

https://www.youtube.com/watch?v=JvBT4XBdoUE