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Difficulty: MediumDeployment Strategy Design

A company is designing a deployment pipeline for a production web application hosted on Amazon EC2 instances inside an Auto Scaling group behind an Application Load Balancer (ALB). The application requires zero downtime during deployments, and the operations team must have the ability to automatically roll back the deployment if new errors are detected via CloudWatch alarms. The team has decided to use AWS CodeDeploy to manage the deployments.

Which two configuration steps should the solutions architect include in the deployment strategy to meet these requirements? (Select two.)

  1. Configure the CodeDeploy deployment group to use a Blue/Green deployment style, and choose the option to copy the existing Auto Scaling group as the replacement environment.Answer
  2. Configure CloudWatch alarms to monitor key application metrics such as HTTP 5xx error rates, and associate these alarms with the CodeDeploy deployment group to trigger an automatic rollback if they enter the ALARM state during the deployment.Answer
  3. C
    Configure the CodeDeploy deployment group to use an In-place deployment style with the CodeDeployDefault.OneAtATime deployment configuration, and configure Amazon Route 53 weighted routing to split traffic between the old and new instances.
  4. D
    Configure the Auto Scaling group's CloudFormation UpdatePolicy to use AutoScalingRollingUpdate with a MinInstancesInService value of 0.
  5. E
    Configure the CodeDeploy deployment group to use a Blue/Green deployment style, and select the CodeDeployDefault.LambdaLinear10PercentEvery3Minutes routing configuration to control the traffic shift.

Answer

To meet the requirements, the solutions architect should configure the CodeDeploy deployment group to use a Blue/Green deployment style that copies the existing Auto Scaling group, and associate CloudWatch alarms with the deployment group to trigger an automatic rollback if they enter the ALARM state.
The correct options recommend configuring a blue/green deployment style by copying the existing Auto Scaling group, and using CloudWatch alarms associated with the CodeDeploy deployment group for automated rollback. Copying the Auto Scaling group ensures a clean replacement environment is provisioned and verified before traffic is shifted, preserving the original environment in case of failure. Associating CloudWatch alarms with the deployment group allows CodeDeploy to monitor the application during and immediately after deployment, triggering an automatic rollback to the original environment if errors exceed defined thresholds.

Step-by-Step Solution

1
Select the appropriate deployment style for zero-downtime and clean rollback requirements.
Determine that a blue/green deployment style using CodeDeploy with a copy of the existing Auto Scaling group provides a separate, clean replacement environment for testing before traffic routing.
An in-place deployment runs the risk of downtime or capacity reduction, whereas a blue/green deployment isolates the new version and ensures the old version remains healthy until traffic is shifted.
2
Select the appropriate mechanism to automate rollback based on post-deployment errors.
Associate CloudWatch alarms monitoring application health and error rates with the CodeDeploy deployment group.
AWS CodeDeploy natively integrates with CloudWatch alarms to monitor deployments. If an alarm fires during the deployment or during the bake time, CodeDeploy will automatically roll back traffic to the blue environment, minimizing the blast radius.
3
Exclude incompatible configuration settings.
Identify that the LambdaLinear deployment configuration is invalid for EC2 deployments, and that setting MinInstancesInService to 0 causes complete application downtime.
Only deployment configurations compatible with EC2/On-premises can be used, and the minimum instances in service must be maintained to satisfy the zero-downtime mandate.

Key Concept

Designing a reliable blue/green deployment strategy for Amazon EC2 Auto Scaling groups using AWS CodeDeploy, including automated rollbacks via CloudWatch alarms.
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Topics

Deployment Strategy Design

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