WarsawJS

For most products, the checkout is the most critical and fragile part of the funnel. It’s where traffic turns into revenue, where small UX regressions compound into large financial losses, and where system failures become immediately visible on the balance sheet. This talk explores how to build resilient, high-converting payment experiences as systems, not screens. Drawing on hundreds of A/B experiments run on tens of millions of users and lessons from operating a global subscription platform generating tens of millions in annual recurring revenue, we’ll look at how payment orchestration evolves as products scale across regions, currencies, and providers. We’ll cover how to design checkout UX that converts consistently even for low-frequency products, how to orchestrate multiple gateways without leaking complexity to the user, and how to test and monitor flows where failure tolerance is extremely low. Along the way, I’ll even show a shocking example where adding just two form inputs, implemented correctly, could cost over a million dollars in lost revenue. This is a practical talk from the trenches about why checkout is a hidden battleground, and how resilient payment engineering protects both conversion and growth.