.tip

Mar 14, 2026 · one of the small things

lsof -i :3000 names the process holding the port

You get "Address already in use" and have no idea what's using it.

lsof -nP -i :3000
kill $(lsof -t -i :3000)

-t prints only the pid, so it's safe to hand to kill. -nP skips the DNS and port-name lookups that make it slow.

shelldebugging

~/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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