> If all of the 2 billion computers in the world produced a new uuidv4 every millisecond, we still wouldn't expect a collision for the next 5 quintillion years.
This would generate 2^127.8 UUIDs.
First, no, the collision would be expected in less than one year, approximately after exhausting square root of the available space (2^64 generated UUIDs): https://en.wikipedia.org/wiki/Birthday_problem
Sure, the presence of some collision somewhere is still likely to happen, but the chances that that collision will actually matter for anything is still vanishingly small.
In the real world, we do not spend 100% of our entire species's computing capacity generating uuids and doing nothing else. In the real world, we aren't burning through uuids at a rate of 2 billion per millisecond, and even if we were it wouldn't matter because the true denominator is the scope of the data system the uuid will be referenced in: if your hard drive partition and my webapp user entry happen to get the same uuid, we will never know, and if for some reason it does matter, then we can use uuidv1 or uuidv7 which guarantee no collisions for thousands of years by embedding a timestamp.
This would generate 2^127.8 UUIDs.
First, no, the collision would be expected in less than one year, approximately after exhausting square root of the available space (2^64 generated UUIDs): https://en.wikipedia.org/wiki/Birthday_problem
Second, no, the UUIDv4 has 122 random bits, not 128 as you thought: https://en.wikipedia.org/wiki/Universally_unique_identifier#...