#refactoring

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I deleted every useMemo and nothing happened

The React Compiler is stable, on by default in new Next.js apps, and supposed to make most manual memoization redundant. I removed 212 useMemo and useCallback calls from a production app to see if that was true. It was, with four exceptions, and the exceptions show what those hooks were really doing.

reactperformancefrontend+1 more

Mar 10, 20268 min10 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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