JSNation Amsterdam

We’ve all shipped something that cost money. An AWS service is left running. A misconfigured webhook. Test keys in production. Small mistakes, varying blast radius. But what happens when a system that serves tens of millions of users per month starts leaking revenue without ringing any alarm bells? Not through a massive crash, those are the easy ones to notice. But through partial failures that look “healthy” in most dashboards. This talk is a case study of a 13-year-old, bootstrapped product that has processed billions of requests, generates tens of millions in annual revenue, and is operated by roughly 10 engineers across the frontend and backend. In 24 hours, on the frontend alone, we can potentially amass over 120,000 errors, generate more logs than we can afford to retain in Datadog for more than two weeks, and other quirks that come with sheer scale. Failures are rarely total. They are regional, conditional, asynchronous, and financially expensive. We will analyze real postmortems in which losses accumulated silently over weeks (one even 9 months). We will explore how architecture across the stack, from React boundaries to API contracts to observability pipelines, determines whether you detect risk early or explain it later. This is not a blame story. It is not a hero story. It is a systems story. Because at scale, software will break. The question is whether your architecture tells you fast enough that it is costing you money and forgives you along the way.