Thanks for sharing EGreg.

Elasticsearch has geo-indexing as well(based on geohash internally), and by default it does id hashing similar to what you said(murmurhash3), we actually leverages that for location based searches.

The challenge addressed in the blog is not in how to search/address(as said Elasticsearch handles it already), it is about how to distribute the load so calculation only happens on limited nodes, and reduce the index size so it can be more performant.