kaiyin.zhong

Writing

Essays

Things I have learned. Things I built, broke, and eventually figured out.

  1. Your primary key knows what time it is Sep 28, 2025 · 11 min UUIDv7 puts a 48-bit Unix timestamp in front of 74 random bits, and that one design decision fixes almost everything wrong with random UUIDs in a B-tree. Postgres 18 ships it natively, from the bit layout down to what it does to the rightmost leaf page. databases · postgres