Usually people say the opposite, logic in db does not scale, though i don't know what scale are they talking about when modern databases (PostgreSQL/MySQL), on

Usually people say the opposite, logic in db does not scale, though i don't know what scale are they talking about when modern databases (PostgreSQL/MySQL), on a single decent box can handle 1M+ TPS (and that is before using replicas to scale reads). As to your comment, nothing is black and white, but if the logic operates strictly on the data (not interfacing with 3rd party systems), having it in the db imo is better/less complex.