[eyelidlessness]

I can’t speak to the implementation but in principle, a filesystem essentially being a specialized database, there’s no reason techniques commonly used for SQL optimization couldn’t be applied here. It’s fundamentally set theory, where you’re obtaining your results by producing subsets rather than traversing a hierarchical tree of branches and end nodes. Of course that implies some pathological conditions (some superset/subset scenarios will produce too many results to be useful or to optimize resolution) which would produce poor UX, but sane defaults and heuristics could alleviate that.

Again not speaking to the project itself, but in principle achieving good performance on something like this would boil down to “do what SQL databases do, then design efficient schemas and queries for the use case”.