It's worth your time to investigate this, it's fixable. Check out mix xref to investigate dependency chains between files in your mix project.

In the project I work on, it turned out a module `use`d by almost every controller included a function (totally unused, btw) which, through a little bit of indirection, caused a circular compile-time dependency between all of them. So any change to any controller caused hundreds of files to rebuild.

Never heard of xref. I'll take a look thanks!

Probably macros.