The correct choice is Stand up a parallel stack with an Application Load Balancer and Auto Scaling group running the new version, then use Route 53 weighted alias records to split and progressively shift traffic between the two load balancers. This option lets you route a small percentage of users to the new build and then ramp to all traffic without downtime while you monitor health and metrics.

Stand up a parallel stack with an Application Load Balancer and Auto Scaling group running the new version, then use Route 53 weighted alias records to split and progressively shift traffic between the two load balancers is effective because you can deploy the new version behind its own ALB and then use Route 53 weighted alias records to apply precise, percentage based traffic splits. You can increase weights as confidence grows and you can roll back instantly by reducing the weight or sending traffic back to the original stack while health checks and monitoring validate the canary.

Configure a private REST API in Amazon API Gateway with an Application Load Balancer integration and create a new stage for the updated build, then use API Gateway canary release to send a small portion of requests to the stage is incorrect because API Gateway private VPC link integrations target Network Load Balancers and API Gateway canaries are designed for API stages rather than general ALB backed web applications.

Use Amazon Route 53 latency-based routing between two Application Load Balancers so that you can gradually move a percentage of users to the new stack is not suitable because latency based routing selects endpoints by measured latency and it does not provide deterministic percentage based splits required for controlled canary rollouts.

Perform a canary deployment with AWS CodeDeploy using the CodeDeployDefault.LambdaCanary20Percent15Minutes configuration is wrong because that preset is for Lambda function deployments and does not apply to EC2 Auto Scaling group or ALB based deployments.

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