#maintenance

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The code nobody read

A client asked me to take over a product two people and an agent had built in four months. It worked. It was sixty thousand lines, no human had read most of them, and the first bug took a week to find because there was nobody to ask. This is what inheriting vibe coded software is like, and what I'd have done differently in those four months.

ai-agentsengineering-practicemaintenance+1 more

Aug 4, 20269 min12 min

~/tips/today — 2026-10-19

~cat tips/today

Never build an index on a live table without CONCURRENTLY

postgresqlmigrations

A plain CREATE INDEX takes a lock that blocks every write to the table for the whole build. On a big table that means minutes of outage that look like a hung app.

CREATE INDEX CONCURRENTLY orders_customer_idx ON orders (customer_id);

It's slower and can't run inside a transaction, so you'll have to tell your migration tool. If it fails halfway, it leaves an invalid index behind, so check pg_index.indisvalid and drop it before you retry.

↵ open y yesterday l ls /tips

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