The lack of an index is not bad at all if you have it stored contiguously in RAM: the mechanical sympathy is great, SIMD will spin like a top not to mention multithreaded programming, etc. Circa 2014 or so I worked on a search engine that scanned maybe 2GB worth of vectors for 10 million documents, queries were turned around in much less than a second, nobody complained about the speed.

If you gotta gather the data from a lot of different inodes, it is a different story.