Yeah, very similar approach. We did this before, see e.g. https://www.stablebuild.com/blog/create-a-historic-ubuntu-pa... - but then figured everyone needs exactly the same packages cached, so why not set up a generic service for that.

For Debian, Ubuntu, and Arch Linux there are official snapshots available so you don't need to cache package downloads yourself. For example, https://snapshot.debian.org/.

Yes, fantastic work. Downside is that snapshot.debian.org is extremely slow, times out / errors out regularly - very annoying. See also e.g. https://github.com/spesmilo/electrum/issues/8496 for complaints (but it's pretty apparent once you integrate this in your builds).

Ubuntu now has snapshot.ubuntu.com, see https://ubuntu.com/blog/ubuntu-snapshots-on-azure-ensuring-p...

Here's a related discussion about reproducible builds by the Docker people, where they provide some more details: https://github.com/docker-library/official-images/issues/160...