From README:

When we remove a package from a repository, it stays in the package
"pool".  We would like to be able to eventually remove packages from
the pool, to reclaim the disk space:

 - `cron-jobs/ftpdir-cleanup`
 - `cron-jobs/db-cleanup`

Both of these programs do the exact same thing.  Parabola developers
decided to write their own from scratch, instead of modifying
`ftpdir-cleanup`.  They should eventually be merged.