Your application receives millions of API requests per second, and you want to manage them effectively. You need a GCP service that allows customization of API behavior without writing code, and also provides analytics, monitoring, and quotas. Which service will you use?

*Explanation: In this scenario, the correct choice is **API Gateway with custom API configurations** (Option A. . This service meets the requirements by allowing you to customize API behavior without the need for writing code. Additionally, it provides essential features such as analytics, monitoring, and quotas, making it the ideal choice for effectively managing a high volume of API requests. Option B, **App Engine with Traffic Splitting**, is not the best choice because it is a Platform-as-a-Service (PaaS) solution and not specialized for API management. Option C, **Cloud Endpoints with Extensible Service Proxy**, would require code for custom behavior, which does not align with your requirement for avoiding code. Option D, **Cloud Run with concurrency settings**, is optimized for container execution and is not the most suitable option for API management in this context. Option E, **Kubernetes Engine with Istio**, is a complex solution and not specifically designed for API management, making it less suitable for this particular use case.*