OP was looking for a fast, indexed search on Mac OSX. ProFind appears to fit the bill. It’s just $6.99.
I’ve tried all of the free alternatives listed on alternativeto.net, but they’re all very slow at indexing, most won’t show when a directory matches, and their interfaces are super clunky.
Using a free trial of ProFind, I was able to index 100k files on a network share in under 5 minutes (others took 20+), and do full searching in under a second. It can match to directories that match your search criteria too! (I don’t work for them, I just did a long search / testing and wanted to share my results for the next person in my shoes)