You don't need a seamless, robust process for dealing with the occasional remote failure (especially when there are mirrors), but you can for example save snaps

You don't need a seamless, robust process for dealing with the occasional remote failure (especially when there are mirrors), but you can for example save snapshots of dependencies. You should be able to do something in an emergency, even if it requires manual intervention. If you can only shrug and wait, that's bad.