.tip

Apr 15, 2026 · one of the small things

Build for the platform you deploy to, not the one you are on

An image built on an Apple Silicon laptop is arm64, and the server is probably amd64. There it runs slowly under emulation, or not at all.

docker build --platform linux/amd64 -t app .

CI runners are usually amd64 already. Locally, set DOCKER_DEFAULT_PLATFORM=linux/amd64 in your shell for the projects that deploy there.

docker

~/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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