I had a course in grad school in which we wrote our own database system, including having to calculate the storage to disk... as in, calculate the sectors, and where you had to break fields to a new sector, and read/write the raw binary data to/from the hard disk.

I have not really had to re-learn file IO since then.

Clearly there are new things to be learned... (do usb sticks even have sectors?)... but having that low-level experience tends to be more than enough for a front-end web developer.