Starting with cachix-action@v14, store paths will be pushed concurrently during CI runs. This drastically reduces the time spent in the post-run step as most paths will have been pushed by the end of the run. We’ve been using this internally for several months now and our post-run times for large rebuilds have gone down from tens of minutes to mere seconds.
This is great. It also means that slow builds can now be resumed. Previously GitHub Actions would timeout on large builds and lose all of the intermediate build results.