[skissane]

The idea that there is a clean distinction between databases and file systems is very POSIX/Microsoft.

On mainframe and minicomputer operating systems they were often far less clearly separated, with a lot of functions which POSIX/Microsoft would view as belonging in a database built into the filesystem – such as record-oriented files and key-indexed files.

That's also true of MUMPS and PICK, which while nowadays language/databases which run on top of a commodity operating system, back in the day were operating systems in their own right.

Maybe some of these old ideas were just bad – or maybe we should reconsider them every now and again?