Learn From Mistakes

Real backend mistakes,
one at a time.

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

By Utsav Rai, backend dev working on production agentic AI in Node/TS.

  1. #0012026-08-08

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

    ADD COLUMN can be instant. AFTER makes it a full table rebuild — and on 100 million rows, a rebuild is a locked table.

    wrong-assumptioncaught by alert2 min lost