Writing our own multi-user code would not be sensible, hence the database. But we could move to a read-only system where the only writing happens on data-import. Then we could use python 'pickle()' or 'json()' read-only data structures, but we -would need to create all our own indexing and cross-referencing code (which is a much bigger job* than you might think). + would need to create all our own indexing and cross-referencing code (which is a much bigger job* than you might think - in fact, it is impossible in a standard wsgi/asgi architecture where there is no shared memory between users and each session is independent).
There would be more lower-level code, but the different segments of the system could be in caving-sensible modules not django-meaningful modules. And we would not have all the extra