‘LocalStore::removeUnusedLinks’ traverses all the entries in /gnu/store/.links and calls lstat(2) on each one of them and checks ‘st_nlink’ to determine whether they can be deleted.
There are two problems: lstat(2) can be slow on spinning disks as found on hydra.gnu.org, and the algorithm is proportional in the number of entries in /gnu/store/.links, which is a lot on hydra.gnu.org. Ludo’.
