Everything in browsers is stupid and awful. IndexedDB is implemented on top of SQLite for Firefox, I think, which makes it completely insane.
And on Chrome it's on a pile of JS on top of LevelDB which...
NoSQL database implemented on top of an SQL database is a fantastic engineering joke but it's truly puzzling how it made it into production. I had to manually vacuum it so that my app stops killing my HDD even after I cleared the IDB completely. There are many reasons Firefox sucks but this one is also funny.