Or some LMDB-backed database, sure. With LMDB you'd essentially map the entire address space of the disk, then just persist pointers. Writes would still not be

Or some LMDB-backed database, sure. With LMDB you'd essentially map the entire address space of the disk, then just persist pointers. Writes would still not be as performant as you would hope, but random read performance would be in the small handfuls of nanoseconds per.