Every time you deploy a snapshot, Artifactory will check the value Max Unique Snapshots for the repository, and if exceeded will mark any excess old snapshots for deletion. Then, every 5 minutes, Artifactory runs a background process that deletes those oldest snapshots that have been marked. For example, if you set Max Unique Snapshots to 5 and deploy a sixth and seventh snapshot to the repository, then the next time the background process runs, it will delete the two oldest snapshots.