An enterprise is deploying an internal microservices application across multiple Google Cloud regions. The application architecture has the following technical requirements: The load balancer must serve private, internal IP addresses accessible to client services within the VPC. Incoming HTTP/HTTPS requests must be evaluated and routed to different backend services based on the URL request path. Backends are distributed across multiple Google Cloud regions to provide low-latency processing by sending requests to the closest healthy backend. If all backend instances in the primary region become unhealthy or overloaded, traffic must automatically fail over to healthy backends in another region. Which load balancing architecture should you deploy to meet these requirements?

A Cross-region internal Application Load Balancer: ### What the Cross-region Internal Application Load Balancer Is A **cross-region internal Application Load Balancer** is a proxy-based **Layer 7** load balancing managed service built on the open-source **Envoy proxy**. It allows organizations to deploy, scale, and manage internal HTTP and HTTPS services using private IP addresses while distributing traffic across backends situated in multiple Google Cloud regions. ### How It Meets the Requirements - **Internal Private Addressing**: It uses internal IPv4 forwarding rules with the `INTERNAL_MANAGED` load balancing scheme, ensuring traffic never traverses or is exposed to the public internet. - **Path-Based Layer 7 Routing**: Being a Layer 7 load balancer, it utilizes **global URL maps** to inspect request attributes (such as hostnames, paths, and headers) and direct traffic to appropriate backend services. - **Multi-Region Proximity Routing**: It distributes traffic to globally distributed backends, automatically directing client requests to the closest available and healthy backend group. - **Automatic Cross-Region Failover**: When all backends within a client's local region fail health checks or reach maximum capacity, the load balancer gracefully spills over or fails over requests to healthy backends in another region. ### Key Advantages and Capabilities - **High Availability**: Protects workloads against single-region infrastructure degradation by routing to alternate regional backends. - **Global Backend Service Scope**: Connects multiple regional instance groups or NEGs to a single shared global backend service. - **Advanced Layer 7 Traffic Management**: Supports traffic steering, header manipulations, and URL rewriting internally. - **Shared Envoy Infrastructure**: Uses dedicated proxy-only subnets in each active region with the `GLOBAL_MANAGED_PROXY` purpose. ### Why This Is Optimal The cross-region internal Application Load Balancer is specifically designed for multi-region internal architectures needing **Layer 7 routing intelligence** and **resilient regional failover** without requiring external exposure or complex custom proxy layers.