Deployment is by far the biggest pain point I've seen in new Elixir developers. Developers use Mix in development, but then build releases using Distillery for production. There are a few gotchas and pitfalls that almost everyone falls into when using Distillery like using `System.get_env` and forgetting `server: true` in their `prod.exs`. Hot upgrades can also be a source of a lot of confusion. Configuring distributed clustering in production can be tricky especially if you're running on Docker/Kubernetes/etc.

That said, I built https://gigalixir.com to try and help with some of these issues and improve the deployment story for Elixir.