I've moved the thumbnails around many times over this project and hopefully it doesn't happen too many more. Once the database has tens of thousands of items, the thumbnails start to become the biggest headache on the disk. Backing up, restoring, and sharding files per directory are slower and more effortful with separate files. In the db means the db is a larger file, but this is disk space that was already getting used anyway. Now it's simpler and has atomic transactions.