[Ukv]

UUIDs are good for creating entries concurrently where coordinating between distributed systems may be difficult.

May also be that you don't want to leak information like how many orders are being made, as could be inferred from a `/fetch_order?id=123` API with sequential IDs.

Sequential primary keys are still commonly used though - it's a scenario-dependant trade-off.

[mkleczek]

If you expose the identifier outside the database, it is no longer "internal".

[Ukv]

Given the chain was:

> > Using a random UUID as primary key does not mean users have to memorize that UUID. [...]

> So what is such an identifier for? [...] Why bother with UUID at all then for internal identifiers?

The context, that you're questioning what they're useful for if not for use by the user, suggests that "internal" means the complement. That is, IDs used by your company and software, and maybe even API calls the website makes, but not anything the user has to know.

Otherwise, if "internal" was intended to mean something stricter (only used by a single non-distributed database, not accessed by any applications using the database, and never will be in the future), then my response is just that many IDs are neither internal in this sense nor intended to be memorized/saved by the user.