I was reading the 12-factor app while thinking about the design of a personal project. I like a lot of what I read, but the following paragraph confused me:
In a twelve-factor app, env vars are granular controls, each fully orthogonal to other env vars. They are never grouped together as “environments”, but instead are independently managed for each deploy. This is a model that scales up smoothly as the app naturally expands into more deploys over its lifetime.
I do not understand what it means for each env var to be "fully orthogonal" to the others. In colloquial usage, I generally think of orthogonality as "being able to change without regard to other items in the collection." However, some things that naturally break into multiple env variables (e.g. database host, port, username, and password) are also quite interdependent.
What does this statement mean?