[mercantile]

From Wiki originally:

> the annual risk of a given person being hit by a meteorite is estimated to be one chance in 17 billion, which means the probability is about 0.00000000006 (6 × 10−11), equivalent to the odds of creating a few tens of trillions of UUIDs in a year and having one duplicate. In other words, only after generating 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%.

So in a theoretical sense, no, but in a practical sense, yes. The same is true for any custom ID format like yours as well. 128 bits is enough to never hit a dup though, so you don't need to go crazy.

Your database should be what authoritatively guarantees uniqueness at the end of the day — generate UUIDs assuming no collisions (which will ~always be true), but store in a UNIQUE index so things'll fail in case of a duplicate or a bug that results in trying to store the same ID twice.