After switching over production traffic to codfw, maps{2007,2010} postgres read replicas look like they are running out of connections.
After some investigation it looks like for some reason on these nodes we have missing indexes.
Specifically these are the missing ones:
planet_osm_line | planet_osm_line_wikidata | CREATE INDEX planet_osm_line_wikidata ON public.planet_osm_line USING btree (((tags -> 'wikidata'::text))) WHERE (tags ? 'wikidata'::text) wikidata_relation_members | wikidata_relation_members_idx | CREATE INDEX wikidata_relation_members_idx ON public.wikidata_relation_members USING btree (wikidata) wikidata_relation_polygon | wikidata_relation_polygon_idx | CREATE INDEX wikidata_relation_polygon_idx ON public.wikidata_relation_polygon USING btree (wikidata)