Nix is primarily a package management tool, yes, but it provides isolation in the sense that you don't have to globally install anything (except for Nix, of cou

Nix is primarily a package management tool, yes, but it provides isolation in the sense that you don't have to globally install anything (except for Nix, of course). A tool I use extensively when developing is a "nix shell", which is a shell that's configured with a `default.nix` file. For example, in project A I use Node.js v12. The project root contains a `default.nix` file that says it needs the package `nodejs-12_x`. When I run `cd /project/root && nix-shell` I'm dropped into a shell that has `nodejs-12_x` along with the rest of my "normal" shell. Once I exit it, `nodejs-12_x` is no longer available. If in project B I use Node.js v14, all I have to do is declare in its `default.nix` file that it uses `nodejs-14_x` and there will be no conflicts whatsoever. Of course this is different from the isolation Docker provides, but I find that for development it is the perfect middle-ground between "everything is installed globally and conflicts with each other" and "everything is so perfectly isolated I can't get anything done".