You have an App Engine application that needs to be updated. You want to test the update with production traffic before replacing the current application version. What should you do?

The correct approach is to deploy the update as a new version within the existing App Engine application and then use App Engine's built-in traffic splitting feature. This allows you to gradually route a percentage of incoming requests to the new version while the majority still goes to the stable, current version. This is a core capability of App Engine designed for canary testing and controlled rollouts. Deploying with Instance Group Updater is incorrect because App Engine manages instances automatically; you don't directly use Instance Group Updater for App Engine version rollouts. Deploying in a new VPC or as a completely new App Engine application, then using global HTTP load balancing, is overly complex and unnecessary. App Engine's native versioning and traffic splitting provide a much simpler and more integrated solution for this use case.