An enterprise has deployed a backend microservice on Cloud Run with its ingress setting configured to internal to prevent direct exposure to the public internet. The security team needs to allow a frontend application running in App Engine standard environment within the same Google Cloud project to privately invoke this Cloud Run service. Which architecture should the security team implement to satisfy these requirements?

Attach the App Engine service to a Serverless VPC Access connector, enable Private Google Access on the connector's subnet, and configure the App Engine service to route all egress traffic through the connector.: ### What the Serverless VPC Access Architecture Is **Serverless VPC Access** bridges Google Cloud serverless runtimes (such as **App Engine standard**, **Cloud Run**, and **Cloud Functions**) to a **Virtual Private Cloud (VPC)** network. Attaching a serverless service to a dedicated connector enables private egress into the VPC without allocating public IP addresses to individual serverless application instances. ### How It Meets the Requirements 1. **Internal Ingress Alignment**: A destination Cloud Run service set to `internal` only accepts requests that originate from inside an authorized VPC network or arrive via approved private paths. Serverless requests must traverse a VPC network to be recognized as internal traffic. 2. **Private Network Path**: Configuring the App Engine service to route `all-traffic` through the **Serverless VPC Access connector** forces all outbound traffic into the VPC subnet. 3. **Private Google Access Enforcement**: Enabling **Private Google Access** on the connector's subnet ensures that requests destined for Google APIs and `run.app` endpoints route privately through Google's internal network infrastructure rather than exiting to the public internet. ### Key Advantages and Capabilities - **Zero Public Exposure**: Eliminates the need for public IP addresses or external internet gateways on either the producer or consumer workloads. - **Granular Egress Control**: Allows centralized firewall rules and route tables to inspect and govern outbound traffic originating from serverless runtimes. - **Seamless Protocol Handling**: Delivers native TLS encryption and identity propagation across serverless services within Google's private backbone. - **Full Enterprise Governance**: Integrates directly with **VPC Service Controls** and organization policy constraints. ### Why This Is Optimal Routing `all-traffic` through the connector while enabling **Private Google Access** on the connector subnet directly fulfills Google Cloud's architectural requirements for serverless-to-serverless internal communication, guaranteeing strict perimeter security without complex reverse proxies.