Probably not strict Elixir related but often our apps use Heroku (or similar) and are cloud-native. It is worth knowing these rules.
The Twelve-Factor App methodology is a methodology for building software-as-a-service applications. It allows you to eliminate the most common problems with our applications. Some of them have already become the industry standard, so you should get to know them all. The methodology constitutes design guidelines strongly focused on cloud-native, portable, and resilient applications.