pub fn prune_expired(db: &Db, now: SystemTime) -> Result<usize>Expand description
Drop the pairings older than the retention window and stamp the ones written before the stamp existed, so they age out one window from the upgrade.
A record this build cannot decode is left alone, the same rule the read path keeps: deleting what cannot be read is how a corrupt row becomes a silent loss. Returns how many rows went.