The Silent Billing Crisis: Why Stripe's Retry Protocol Defeated HTTP Convention

This incident exposes a critical gap between how developers typically interpret HTTP status codes and how Stripe's webhook protocol actually works. Unlike standard APIs where 4xx signals 'client error, don't retry,' Stripe treats any non-2xx response as a delivery failure worthy of exponential backoff retries. When combined with monthly-only invoice events that naturally evade detection gaps, a single database lookup failure can silently break billing for days before the platform warns of auto-disablement—making webhook error handling a business-critical concern for any SaaS built on subscription revenue.