.tip

Sep 3, 2026 · one of the small things

Copy the lockfile before the source in a Dockerfile

Every layer after a changed file gets rebuilt. If COPY . . comes before pnpm install, a one line code change reinstalls everything.

COPY package.json pnpm-lock.yaml ./
RUN pnpm install --frozen-lockfile
COPY . .

Now the install layer stays cached until a dependency changes, which happens a few times a month and not a few times an hour.

dockerci

~/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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