Ask HN: How do you track what's backed up?

A data inventory should be the source of truth, which should flow into backup strategy and technical implementation details. You cannot backup (or manage the lifecycle of) what you do not know you have or aren't tracking.

backup is half the job...the other half is testing the backup (ie. get to a working environment with just the backup)

It is great you implemented backups but as someone in the comments has already said make sure they are tested. Also, remember about recovery capabilities. I mainly use GitProtect.io as it covers my entire stack, allows me to oversee all the processes, works in accordance with the 3-2-1 backup rule and is automated too. So yeah, in terms of tracking backups, that tool resolves my issues as there is a central management console where you manage everything from one place.