Most tutorials show you how to build an API. Fewer show you what sits in front of the API in a real production system. This project is about that middle layer. A gateway that all requests go through before they reach the actual API. It checks authentication, enforces rate limits, and routes traffic. In Azure this is what API Management does. Here it runs locally with YARP, Microsoft's open source reverse proxy library. The actual application is a travel booking system. The gateway pattern is the interesting part. Why a gateway matters When you build an API and expose it directly to clients, every client knows your API's address. They can call it as many times as they want. There is no central place to enforce authentication or throttle abusive callers. A gateway changes that. Clients only know the gateway address. The API address is internal. The gateway handles auth and rate limiting before requests ever reach your code.…