ethan_smith parent
UUID v4 has 122 random bits giving 2^122 possible values (~5.3×10^36). Using the birthday paradox, you'd need to generate about 2^61 UUIDs (~2.3×10^18) for a 50% collision probability, which is well beyond any practical system's capacity.
> ...which is well beyond any practical system's capacity.
Well beyond a single server but not single systems. Large analytical data models run into the tens of exabytes in practical systems already. It isn't hypothetical and probabilistic identifiers become inadvisable[0] in those systems.
Not everything is a web app and UUIDv4 does not scale infinitely.
[0] Technically you can use probabilistic identifiers if you widen them beyond 128-bits, but at that scale the compactness of unique identifiers has a large impact on performance and cost, so 128-bit deterministic identifiers are preferable.