That query would be this: SELECT json_field FROM data WHERE json_field->'age' > 15 Part of the performance increase for hstore is improvements for GIN indexes

That query would be this: SELECT json_field FROM data WHERE json_field->'age' > 15 Part of the performance increase for hstore is improvements for GIN indexes, and according to the author can be applied to json. So yes you can use indexes on your hstore or json documents.