https://github.com/Commonists/fastcci is a fast in-memory database server that can perform category inspections. Currently implemented is super-fast infinite depth category intersection, infinite depth category traversal (listing). I'm working on 'NOT' operations (in CAT1 but not in CAT2).
This is a backend for a category search I intend to introduce on Wikimedia commons.
Applications include finding 'Featured Pictures' or 'Quality Images' within category trees, Images within category trees that are not in 'Media with Locations' etc.
I need an instance with about 1-2GB RAM. The cat tree for commons currently occupies about 600MB. Further instances could be created to offer category intersection to other projects.
The fastcci database could also be used as a backend to other search tools.
