Create a grid in PostGIS for CARTO based off of arbitrary envelope and Projection

grid.sql

INSERT INTO <my_table_name> (cartodb_id, the_geom, the_geom_webmercator)
WITH inputs AS (SELECT     
  ST_Transform(ST_SetSRID(ST_MakeEnvelope(
    -126.21093749999999, 23.241346102386135,
    -63.28125, 50.064191736659104
  ), 4326), 5070) geom,
  500000 width,
  500000 height
), rast AS (SELECT
  (st_pixelaspolygons(
    st_addband(
      st_makeemptyraster(
        ((st_xmax(geom) - st_xmin(geom)) / width)::int,
        ((st_ymax(geom) - st_ymin(geom)) / height)::int,
        st_xmin(geom), st_ymax(geom), width::numeric, -height::numeric,
        0.0, -- skew x
        0.0, -- skew y
        st_srid(geom) -- srid
	  ), 1, '2BUI', 1
    ), 1, False
  )).geom FROM inputs
)
SELECT row_number() over () as cartodb_id,
       st_transform(geom, 4326) as the_geom,
       st_transform(geom, 3857) AS the_geom_webmercator
FROM rast