Ok so if we take this repo and then the headline from https://news.ycombinator.com/item?id=41085376, we could get an infinitely fast file system by just putting another SQLite filesystem on top.
Why would you bother with this instead of just making an in memory drive? I remember mounting in memory drives even in MS-DOS back in the early 90s. I did it to move whatever game I wanted to play into the RAM Drive so my load times would be faster.
Which was essentially SQL Server as a filesystem.
Project was ultimately cancelled.
https://en.m.wikipedia.org/wiki/WinFS
I think you're confusing the fact that an application uses data structures with that application being like a database.