A company has a Node.js application deployed in an Elastic Beanstalk environment. At the moment the environment uses an “All at once” deployment strategy. The new versions are deployed in all instances simultaneously and there is an outage for a short time. If there is a problem with the new version, another deployment is required to perform a rollback. Your manager asks you to use another method that deploys newer versions to a fresh group of instances and the new instances should serve traffic only after the health check has passed. In the meantime, you do not want to maintain two environments in Elastic Beanstalk. Which deployment strategy should you select?

Answer options:

A.Configure a Rolling update strategy in the Elastic Beanstalk environment. Deploy newer application versions on newer instances and then attach those instances to the original load balancer.
B.Set up a Rolling with additional batch strategy which launches an extra batch of instances for new deployments.
C.Configure a blue/green deployment strategy by swapping environment URLs in Elastic Beanstalk.
D.Configure an Immutable deployment strategy in the Elastic Beanstalk environment.

Correct Answer – D
In order to deploy new versions in new instances, the Immutable deployment strategy should be chozen. The references can be found in https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features.rolling-version-deploy.html and
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/environmentmgmt-updates-immutable.html.
Option A is incorrect: For Rolling update, the original instances are detached from the load balancer for the deployment. This update strategy does not create new instances.
Option B is incorrect: The Rolling with additional batch strategy still performs the deployments in existing instances although it creates another batch to maintain full capacity.
Option C is incorrect: For the swapping environment URLs feature in blue/green deployments, two environments are required in Elastic Beanstalk. It does not meet the requirement of the question.
Option D is CORRECT: With Immutable deployment, a second, temporary Auto Scaling group with new instances is created for the update. The deployments are immutable and not performed on old instances.