Hi cwmma. RethinkDB actually does use Hilbert curves at multiple scales for indexing geometry. The implementation for this mapping comes from Google's S2 library. You can find the details documented in Google's code: https://code.google.com/p/s2-geometry-library/source/browse/...

We looked into some other data structures before settling for our current approach. Using a space-filling curve turned out to be the least error-prone to implement given that we already have a highly optimized and well tested btree implementation in RethinkDB.