Problem with Docker is that it abstracts away one level too much. Somehow it's there to provide container isolation but in an abstraction that almost feels like

Problem with Docker is that it abstracts away one level too much. Somehow it's there to provide container isolation but in an abstraction that almost feels like a VM. So caching is pretty hard, in fact caching is more or less based on the source code layout. Nix doesn't provide this level of isolation, it doesn't pretend to provide a separate machine. Which allows caching of packages, thus eating less disk space and making rebuilds faster. Not sure how Nix(OS) handles isolation in terms of cgroups/namespaces though, seems that it relies on systemd for that.