insert into 
    hexgrids (id, params, tag)
    values
    (
        1,
        (
            hex_OrientationFlat(),
            3857,
            ST_SetSRID(ST_MakePoint(0, 0), 3857),
            ST_SetSRID(ST_MakePoint(500, 500), 3857)
        )::hexgrid,
        'flat_grid_500x500'
    ),
    (
        2,
        (
            hex_OrientationFlat(),
            3857,
            ST_SetSRID(ST_MakePoint(10, 20), 3857),
            ST_SetSRID(ST_MakePoint(20, 10), 3857)
        )::hexgrid,
        'flat_grid_20x10'
    );
select ST_SetSRID(ST_MakePoint(10000, 10000), 3857)::hexagon as hexagon;
 hexagon 
---------
 (115,1)
(1 row)

select ST_AsText(ST_Centroid((28, 1)::hexagon)) as center;
            center            
------------------------------
 POINT(4500 4330.12701892219)
(1 row)

select ST_AsText(ST_Transform(
    (ST_Hexagon(ST_SetSRID(ST_MakePoint(-73.0, 40.0), 4326), 1))::geometry, 4326
)) as geom;
                                                                                                                              geom                                                                                                                              
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 POLYGON((-72.9970999875523 40.0017510726044,-73.0015915639729 40.0017510726044,-73.0038373521832 39.9987713095566,-73.0015915639729 39.9957914164756,-72.9970999875523 39.9957914164756,-72.994854199342 39.9987713095566,-72.9970999875523 40.0017510726044))
(1 row)

select
    morton_unpack((ST_Hexagon('SRID=3857;POINT(13 666)', 2)).code) as p1,
    morton_unpack((ST_Hexagon('SRID=3857;POINT(666 13)', 2)).code) as p2,
    morton_unpack((ST_Hexagon('SRID=3857;POINT(-13 -666)', 2)).code) as p3,
    morton_unpack((ST_Hexagon('SRID=3857;POINT(-666 -13)', 2)).code) as p4;
   p1   |    p2    |    p3    |   p4    
--------+----------+----------+---------
 {0,37} | {22,-11} | {-1,-39} | {-22,9}
(1 row)