When deleting a snapshot we accumulate in memory a list of all the blobs that can be deleted after the repository update is committed. Each blob name takes only ~80B of heap, but it's possible for there to be very many blobs (it's theoretically unbounded). I've seen ~100M blobs to be deleted in practice, which can add up to several GiBs of heap in total. We should find a way to track this work with bounded heap usage.