Where to store key or certificate files?

Question

Ruby on Rails

In general, there are third-party service key files.
In one of the projects I met how they were stored in the root of the application (in a folder).
I met that they were stored in db/ssl/client.key
A in fact how (can store keys in environment variables) and where is it better to store such files?

Answer 1

On production. Not in the repository.

Answer 2

In a special infrastructure repository in encrypted form.
In this repository you keep scripts/manifests to set up your servers for the application.