To clarify; we (including @shyamd, myself) don’t use pymatgen-db anymore, but some people do, including some of the original maintainers. We don’t encourage it for first-time users.
We still use MongoDB extensively to query and back up our calculations however, we just use the “VaspDrone” in atomate to do so: https://github.com/hackingmaterials/atomate/blob/master/atomate/vasp/drones.py
The VaspDrone can take a directory from a VASP calculation and convert it into a Mongo-style document for you.