It seems it's using `better-sqlite3`[0] and saving the database to a file called "private/unforget.db"[1].
(Although, I don't have experience with SQLite, so that file might be as volatile as `localStorage`.)
[0] https://www.npmjs.com/package/better-sqlite3
[1] https://github.com/computing-den/unforget/blob/master/src/se...