Building a Production-Ready API Gateway: From Token Bucket Rate Limiting to JWT Validation

Your microservices architecture is humming along until Black Friday hits. Suddenly, a single misbehaving client hammers your checkout service with 10,000 requests per second, cascading failures across your entire platform. You scramble to add rate limiting, but where exactly should it live, and how do you implement it without becoming a bottleneck yourself? This scenario plays out more often than engineering postmortems admit. The instinct is to bolt rate limiting onto each service—a few lines of middleware here, a Redis counter there. But now you're maintaining identical logic across fifteen services, each with slightly different implementations, none of them coordinated. When the next incident hits, you discover that your payment service allows 100 requests per second while your inventory service allows 50, and attackers have found the gap. The answer isn't more distributed logic. It's centralization done right. An API gateway sits at the edge of your infrastructure, intercepting eve