Ask HN: We just had an actual UUID v4 collision...

·Hacker News··

I know what you're thinking... and I still can't believe it, but...This morning, our database flagged a duplicate UUID (v4). I checked, thinking it may have been a double-insert bug or something, but no.The original UUID was from a record added in 2025 (about a year ago), and today the system inserted a new document with a fresh UUIDv4 and it came up with the exact same one:b6133fd6-70fe-4fe3-bed6-8ca8fc9386cdWe're using this: https://www.npmjs.com/package/uuidI thought this is technically impossible, and it will never happen, and since we're not modifying the UUIDs in any way, I really wonder how that.... is possible!? We're literally only calling:import { v4 as uuidv4 } from "uuid";const document_id = uuidv4();... and then insert into the database, that's it.Additionally, the database only has about 15.000 records, and now one collision. Statistically... impossible.Has that ever happened to anyone?! What in the...

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