UUIDs are integers, they just happen to be 128 bits long instead of the more common 32 or 64, and they are usually printed in a specific way that differs from how integers are usually printed. But that's just smoke and mirrors.

UUIDs are generally not guaranteed to be universally unique. The name is misleading marketing.

If you generate them randomly, then the probability of collision is small enough not to matter, but the more you introduce deterministic elements, like generating them sequentially, the more your probability of collision increases.

Yes, of course. But making them sequential does not take away from the universal(ish) uniqueness

Meant ordered here, not sequential.

Is this sarcasm? If you generate an incrementing-UUID then its predictability is going to make it not-universally unique too

No. Incrementing an integer might be unique for the local database, but not unique for the universe.

That is…not what universally unique means.

From RFC4122: "A UUID is an identifier that is unique across both space and time, with respect to the space of all UUIDs."

Hard to achieve if everyone starts from 00000000-0000-0000-0000-000000000000.

Right that’s why nobody starts at 0. And you don’t have to only add 1 to be ordered, no DB I’m aware of just adds 1 to sequential UUIDs. There’s always randomness/entropy involved.

Sequential UUIDs don’t start at 0. They are a 128-bit composite of two integers; a temporal component in the high order bits and a random component in the low order bits.

UUIDs are just 128-bit simple integers.