Your backend returned 200. The mobile app showed an error. The user tapped "Pay" three times. Three pending charges hit their account. One order was placed. Their balance was short. And your incident log showed zero failures. Every engineer on the team did their job. Nobody solved the problem. This is the most common way engineering teams fail, not through incompetence, but through excellent execution of the wrong unit of work. And until you recognise the difference between compl...