You want to deploy app updates and route a small portion of real user traffic to the new release while most users stay on a stable version. What should you do?

The correct option leverages App Engine's built-in traffic splitting feature, which is designed precisely for this scenario. By deploying a new version within the same App Engine service, you can easily configure a small percentage of user traffic to be routed to the new version, allowing for canary deployments or A/B testing without impacting the majority of users. The incorrect option suggesting a new service for each update is less efficient because services are typically used to separate distinct functional components of an application, not for rolling out minor updates to the same component. The GKE options are incorrect because while GKE can support similar blue/green or canary deployments, App Engine offers a more direct and managed solution for traffic splitting at the application level, making it the most suitable choice for this specific requirement.