If a website runs on Azure App Service and needs routing based on HTTP request attributes, which Azure service should be added?

Azure Application Gateway is the correct choice because it operates at Layer 7 (HTTP/HTTPS) and provides advanced traffic management capabilities such as URL-based routing, cookie-based session affinity, and Web Application Firewall (WAF) integration. This allows it to route requests based on HTTP attributes like URL paths or host headers, which is precisely what the question asks for. Azure Load Balancer operates at Layer 4 (TCP/UDP) and performs basic, non-HTTP-specific load distribution. Azure Front Door is a global, scalable entry point that uses Layer 7 capabilities but is primarily for global routing and content delivery, not for routing within a single region's application. Azure Traffic Manager is a DNS-based traffic load balancer that distributes traffic at the DNS level, not based on HTTP request attributes.