DOP-C02 Incident and Event Response Practice Question
During a deployment, a new application version on an ECS service starts failing health checks. The previous version is still running. The deployment is a rolling update with a 200% percent start. Which ECS feature should the engineer use to automatically revert to the previous version?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ECS deployment circuit breaker
(ECS deployment circuit breaker) is correct because it automatically detects failed deployments (e.g., health check failures) and triggers a rollback to the previous version. With a 200% percent start rolling update, the new version starts before the old is stopped; if health checks fail, the circuit breaker initiates a rollback. Option B (ECS service auto recovery) recovers from underlying infrastructure failures, not deployment failures. Option C (ECS managed scaling) adjusts desired count based on load, not deployment health. Option D (CloudWatch alarm actions) can trigger rollback events but is not an ECS built-in feature; it requires custom automation. Therefore, the correct ECS feature for automatic rollback is the deployment circuit breaker.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ECS deployment circuit breaker
Why this is correct
The ECS deployment circuit breaker is a native ECS feature that continuously monitors the health of a service deployment by watching for failed health checks, crashes, or task startup failures. If it detects that the new version is unhealthy, it automatically cancels the deployment and rolls back the service to the previous stable revision, without manual intervention. This makes it the only option that directly addresses deployment failures as part of the ECS service update path.
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ECS service auto recovery
Why it's wrong here
ECS service auto recovery, also known as automatic recovery for Amazon ECS, detects when a task or the underlying EC2 instance fails due to hardware or infrastructure issues and restarts the affected tasks on a healthy host. It does not evaluate deployment progress, validate a new task definition, or trigger a rollback when an application version fails to deploy. Consequently, it is effective for instance-level resilience but entirely unrelated to deployment failure handling.
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ECS managed scaling
Why it's wrong here
ECS managed scaling leverages Application Auto Scaling or Cluster Auto Scaling to adjust the number of running tasks based on demand metrics such as CPU utilization, memory pressure, or request count per target. It neither monitors the health of an actively updating deployment nor decides whether a new task definition is fit for production, and it cannot revert to a prior version when a rollout fails. Therefore, while it maintains capacity, it is not a deployment health mechanism.
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CloudWatch alarm actions
Why it's wrong here
CloudWatch alarm actions allow you to invoke an action, like an auto scaling policy or an SNS topic, when a metric threshold is breached, but ECS does not natively treat a CloudWatch alarm as a deployment rollback signal. To perform a rollback with CloudWatch, you would need to custom-build a Lambda function or a separate orchestration process that modifies the service, which is neither native nor automatic to the deployment lifecycle. The deployment circuit breaker, in contrast, integrates alarm monitoring directly into the ECS update process.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DOP-C02 exam.