Your company has an application running on App Engine. They want to integrate machine learning models and require minimal code changes. They also want the ability to version these models. Which service would you recommend?

*Explanation:* To integrate machine learning models into an App Engine application with minimal code changes and versioning capabilities, **AI Platform Prediction with App Engine** is the recommended service. AI Platform Prediction allows you to deploy and serve machine learning models seamlessly with App Engine while offering versioning for models. This integration ensures that your application can leverage machine learning without significant code modifications, making it an efficient choice for your requirements. The other options may involve more complexity or are not as well-suited for this specific use case.