I experimented with geospatial Hilbert Curves as a Postgres extension [0] for PostGIS using the S2 [1] spherical geometry library. S2 uses a scale free cell coverage pattern that is numbered using six interlocking space filling Hilbert Curves [2]. This approach is similar to what is used in this article. S2 doesn't use hexagons but a different cell structure but the idea is generally the same.
By having both high level (cell) and low level (cell id) geometries it was a very powerful library which allowed projection from the hilbert space into a Postgres spatial index (spgist) including various trees, like noted in this article. It appears to be still quite active in development.
By having both high level (cell) and low level (cell id) geometries it was a very powerful library which allowed projection from the hilbert space into a Postgres spatial index (spgist) including various trees, like noted in this article. It appears to be still quite active in development.
[0] https://github.com/michelp/pgs2
[1] https://s2geometry.io/
[2] https://s2geometry.io/devguide/s2cell_hierarchy