Question 1

Can the same UUID be generated twice?

Accepted Answer

In practice, no. v4 carries 122 bits of randomness; the collision probability stays negligible even after generating billions of them.

Question 2

Should I use a UUID as a primary key?

Accepted Answer

They're valuable in distributed systems and when the client must mint the ID. But random UUIDs aren't sequential in an index and hurt write performance on large tables; a time-ordered variant such as UUIDv7 solves that.

UUID Generator