Learn From Mistakes

Not tutorials. Each post is one thing I got wrong in production: what broke, what I wrongly believed, what was actually happening underneath, and the rule I follow now. One a week.

By Utsav Rai, backend dev building production agentic AI in Node/TS. Most engineering writing shows the finished thing and skips the six hours someone spent believing something false. That gap is the useful part.

1 mistake2 min lostwrong-assumption × 1
  1. #0012026-08-087 min

    One keyword turned an instant migration into a two-minute outage

    ADD COLUMN can be free. AFTER makes it copy every row. On ~100 million rows that's a locked table, and MySQL picks between the two silently.

    wrong-assumptioncaught by alert2 min lost