The “primary key” of any and every(!) table within your database should be a perfectly-arbitrary, yet guaranteed-unique, “identifier ... and nothing more™ ...” of a particular row. All such values should be entirely internal to the database, and never exposed to, therefore also never of material interest to, the outside world.

This touches on the general question on whether or not to use Natural Keys [1]. Apparently you think one should not use natural keys. You think surrogate keys are always necessary.

That's fine, but it certainly isn't received wisdom. It is an open question: many people will argue that natural keys have important advantages [2]. I will always use natural keys where possible.

[1] https://en.wikipedia.org/wiki/Natural_key

[2] http://www.databasesoup.com/2015/03/primary-keyvil-reprised.html