The math says no. UUID v4 has 122 bits of randomness, so collision probability for 15K records is N²/(2·2^122) ≈ 2·10^-29. That's somewhere around "fewer collisions per universe lifetime than atoms in your liver." Whatever you're seeing, the culprit is overwhelmingly somewhere else.

Things to check, in descending order of how likely they actually are:

1. Data import / migration / backup restore, perhaps? Did anyone load a CSV, run a seed script, restore a snapshot, or copy rows between environments at any point in the last year? This is what "duplicate UUID" is in 99% of cases. Check git on migrations, ops history on the DB, and ask anyone who might have been moving data around.

2. Application retry / rollback bug maybe? Code path that generates a UUID, attempts insert, fails on constraint violation, retries with the same UUID variable still in scope. Check whether UUID generation lives inside or outside the retry boundary.

3. Older versions of the uuid package in certain bundler environments would fall back to Math.random() instead of crypto.getRandomValues(). What version are you on? Anything <4.x is suspect; modern v8+/v9+ uses crypto everywhere correctly.

4. Could also be a process fork bug. If a UUID generator runs in a child process spawned from a parent that already used the PRNG, the entropy state can get copied. Rare in Node specifically, more historical in old Python/Ruby setups.

If you've ruled all of those out and the row really was generated independently a year apart via crypto.getRandomValues, go buy a lottery ticket. But it's almost certainly cause #1.

Statistically speaking, does extremely unlikely mean impossible? If it were replicable I'd raise my eyebrow, otherwise it's fair game, no?

As someone that enjoys the unterminable complaints about RNG in the video game scene, I would never trust any human's rationalization of random outcomes.

There could be a problem with the way the system generates entropy for randomness.

Question to fellow HNers, do you recognize that this comment was written by AI?