.tip

May 21, 2026 · one of the small things

X-Content-Type-Options and Content-Disposition on user uploads

Say a user uploads an HTML file called photo.png. A browser that sniffs content types will render it, with your origin's cookies attached.

X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="photo.png"

Serving uploads from a separate domain is better still. If they share yours, these two headers are the minimum.

securityhttp

~/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

esc close