Exam AWS Certified DevOps Engineer - Professional DOP-C02 topic 1 question 332 discussion

When the DevOps engineer deploys a new version of the ECS service (e.g., with a new container image), the ECS tasks might take some time to become healthy and respond to ALB health checks successfully. During this period, the ALB health checks could fail if they are not given enough time to detect the new tasks' readiness. By increasing the ALB health check grace period, the engineer ensures that the new tasks have enough time to start up and become healthy before the ALB marks them as unhealthy. This can prevent the tasks from frequently stopping and starting due to health check failures.

aws elbv2 modify-target-group-attributes \ --target-group-arn <target-group-arn> \ --attributes Key=health_check.grace_period,Value=<desired-value>

B - ALB health check is failing the new task

"A" is wrong because in the question it's said that Engineer has only updated image in the task definition. So he could not affect security group. "B" might be correct explanation, because new Docker container (based on a new image) takes longer time to start. So increasing a grace period might help to eventually get a successful health-check result and quit restarting the container.

B