#on-call

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Letting an agent touch production

Over five months we gave an agent access to production on-call in stages: read only, then propose, then act on a short list, then act on a longer one. Each stage had to prove a specific thing before the next. The rules that came out of it fit on a page, and they aren't the ones I'd have guessed at the start.

sreai-agentson-call+1 more

Aug 25, 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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