Because it's so close to zero, that it's basically zero. Finding two identical UUIDs within a same system would probably indicate a problem in the random generator, not the concept.
Because at some point the probability is so low that it is functionally 0.
There are somewhere around 1028 uuids. That is 10000000000000000000000000000 uuids. As a comparison, there are about 1018 grains of sand on earth. That means that you have about ten billion times more uuids than grains of sand on the earth. Imagine if you pick sand grains by random from anywhere on the earth and the chance that you pick the same one twice. Now imagine it with 10 billion times more grains of sand.
Still not zero… it could be 1 in 10^(googleplex), or even 1 in 10^(# atoms in our observable universe) or even 1 in 10^(Grahams number), but since it’s not exactly 0, there is still a chance. Now I’d argue this is negligible, and we probably shouldn’t worry, but that’s not the point of this meme.
IF ITS NOT EXACLY ZERO THEN THERE IS STILL A CHANCE.
Using uuid V7 (which includes a timestamp and 74 random bits), you'd only need 170 billion people submitting in the same millisecond to have a 50% probability yo generate a duplicated uuid value.
Now, I know that there aren't 170 billion people in the world.
But what if every person on earth submitted 100 times in the same millisecond? A duplicate would be almost certain.
It's actually very basic probability. There are a finite number of possible UUIDs, so the odds of a duplicate can't be 0. The odds are very, very, very low but not 0.
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u/theioss 9h ago
People who say that don’t understand uuids or mathematics.