Great talk here from HCA Healthcare about their architecture and tech stack using Elixir OTP, Riak:

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

TL;DR - Elixir/OTP for fault tolerance and process supervision, Riak as a KV store (no other database) and an interesting process-actor model for patients I found delightful. Bonus: hot code patching, zero downtime