Failure Is the Default

1. The Three Ways a Call Fails

When Checkout calls Payments, three things can go wrong. They are not equally dangerous.

1. Fast failure. Payments returns an error right away: connection refused, a 500 status, or "service unavailable." This is the kindest failure. The caller learns the truth quickly and can react to it. Fast failures cost almost nothing each time they happen.

2. Slowness. Payments still answers, but it takes 30 seconds instead of 200 milliseconds. This is the failure that takes systems down. Understanding why is the core insight of the whole module.