Test Update with Production Traffic

B.

The correct answer is B: Deploy the update as a new version in the App Engine application, and split traffic between the new and current versions.

Explanation: When you want to update an App Engine application, it is recommended to use a new version for the updated application. A new version allows you to test the update with production traffic before replacing the current application version. Splitting traffic between the new and current versions allows you to gradually shift traffic to the updated version, reducing the risk of errors or downtime.

Option A, deploying the update using the Instance Group Updater to create a partial rollout, which allows for canary testing, is not the recommended approach for updating an App Engine application. The Instance Group Updater is used for updating Managed Instance Groups, which is not applicable to App Engine applications.

Option C, deploying the update in a new VPC and using Google's global HTTP load balancing to split traffic between the update and current applications, is not recommended for App Engine applications because App Engine is a fully managed serverless platform that does not require you to manage infrastructure like VPCs.

Option D, deploying the update as a new App Engine application and using Google's global HTTP load balancing to split traffic between the new and current applications, is not the recommended approach because it requires more configuration and setup time, and could introduce potential issues with maintaining two separate applications.

In summary, the recommended approach for updating an App Engine application is to deploy the update as a new version and split traffic between the new and current versions.