The primary key serves a database function, and its data type should be optimized to suit that function. If you need an enumeration resistant id for public use,

The primary key serves a database function, and its data type should be optimized to suit that function. If you need an enumeration resistant id for public use, a uuid is a great idea, but it's a mistake to make the primary key in a database do double duty as a public identifier and impose inappropriate constraints on it as a consequence.