How snapshots work

A snapshot records the profile's counts and up to 500 follower and 500 following identities at the moment it runs. The 500-per-list cap is a real bound: for larger accounts the snapshot's follower list is genuinely partial, and the coverage badge shows exactly what fraction it captured.

Capture one from the History tab of any profile. Each snapshot writes its own row, plus membership rows for every identity it saw. Two consecutive snapshots' membership rows are what the diff engine reads.

There is no scheduler in this build. A profile you're tracking only gets a new snapshot when someone opens its History tab and captures one manually.