Engineering notes
How BuildAPI works underneath, what we got wrong, and what we changed. Written by the people who broke it.
Tests that fail when you break them
A passing test proves nothing until you have watched it fail for the right reason.
What a fresh install should look like
Correct on arrival, not correct after something repairs it.
A quote and a charge must be one number
The moment those are two implementations, they diverge — and the customer finds out at the card.
The cron that nobody scheduled
Background work that only runs when someone visits is not background work.
Bound, verified, enforced: three states people read as one
A key's relationship to a domain has three separate properties, and conflating them causes most of the confusion we see.
Entitlement tokens, explained
The mechanism that keeps your site up during our outage, and how to use it properly.
Pricing in one currency, charging in another
We quote in dollars and charge in naira. Almost every bug we shipped this year lived in that gap.
Designing a refusal message
Most systems tell the user what happened. Good ones tell them what to do.
Rotating a key without downtime
The sequence matters. Done in the wrong order, rotation is an outage.