I’m not an expert in mono repos but I’ll answer as best I can. First, I don’t think they are meant for checking in all your external dependencies, it’s for putting all your source code (for your company, project, etc). If you are going to modify/fork an external project, then yes, otherwise just use the standard package manager. If two projects depend on two different versions of another module that’s part of your monorepo, you will need develop them on two different branches. I think the idea of a monorepo is that you want all your code to be in sync. You want to strive to converge everything towards the master branch. In reality that may not be practical, in that case, you can treat a module as an external dependency and version it independently. Hope that makes some sense.