New best story on Hacker News: Ask HN: We just had an actual UUID v4 collision...
Ask HN: We just had an actual UUID v4 collision... 418 by mittermayr | 318 comments on 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-bed6-8ca8fc9386cd We're using this: https://ift.tt/wjoZnrU I 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....