The correct answer is to configure the ECS service to run tasks in at least two Availability Zones and enable the ECS service auto-recovery feature. This works because ECS Fargate AZ rebalancing is a built-in mechanism that automatically detects when tasks are concentrated in fewer AZs than intended—such as after an entire zone fails—and proactively launches replacement tasks in the remaining healthy zones to restore the desired count and distribution. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this concept tests your understanding of how ECS service auto-recovery differs from simply setting a multi-AZ deployment; a common trap is assuming that deploying across multiple AZs alone is sufficient, but without enabling auto-recovery, the service will not automatically replace tasks lost to a zone failure. For a memory tip, think of it as “two AZs plus auto-recovery” — the service needs both the spread and the self-healing trigger to survive an AZ outage without manual intervention.
DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs a critical application on Amazon ECS with Fargate launch type. The application is deployed across multiple Availability Zones. The DevOps team needs to ensure that if an entire Availability Zone fails, the application continues to serve traffic without manual intervention. What should the team do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the ECS service to run tasks in at least two Availability Zones and enable the ECS service auto-recovery feature.
Option C is correct because the ECS service's AZ rebalancing feature automatically redistributes tasks across Availability Zones when an imbalance is detected, such as after an AZ failure. By configuring the service to run tasks in at least two AZs and enabling this feature, the ECS service will automatically launch replacement tasks in the remaining healthy AZs to maintain the desired count, ensuring continued traffic serving without manual intervention.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use an Amazon ECS service auto-scaling policy to automatically replace tasks in the failed AZ.
Why it's wrong here
Auto-scaling does not automatically redistribute tasks across AZs.
✗
Configure the ALB to enable cross-zone load balancing and enable the ECS service's AZ rebalancing feature.
Why it's wrong here
ECS does not have an AZ rebalancing feature; ALB cross-zone is not enough.
✓
Configure the ECS service to run tasks in at least two Availability Zones and enable the ECS service auto-recovery feature.
Why this is correct
Multi-AZ deployment plus auto-recovery ensures resilience.
Related concept
Read the scenario before looking for a memorised answer.
✗
Set the ECS service's minimum healthy percent to 100 and maximum percent to 200.
Why it's wrong here
This helps during deployments, not AZ failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse auto-scaling (which adjusts capacity based on demand) with AZ rebalancing (which redistributes tasks after an AZ failure), leading them to choose Option A or B, or they mistakenly think deployment configuration settings like minimum/maximum percent (Option D) can handle AZ failures.
Detailed technical explanation
How to think about this question
The ECS service's AZ rebalancing feature works by monitoring the distribution of tasks across AZs and, when an imbalance is detected (e.g., due to an AZ failure), it automatically launches replacement tasks in the remaining healthy AZs to restore the desired count. This feature is enabled by default for services using the Fargate launch type and requires the service to be configured with tasks in at least two AZs. Under the hood, ECS uses the Amazon ECS service scheduler to detect task failures and rebalance tasks, leveraging the underlying infrastructure of AWS Fargate to provision new tasks in healthy AZs without manual intervention.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the ECS service to run tasks in at least two Availability Zones and enable the ECS service auto-recovery feature. — Option C is correct because the ECS service's AZ rebalancing feature automatically redistributes tasks across Availability Zones when an imbalance is detected, such as after an AZ failure. By configuring the service to run tasks in at least two AZs and enabling this feature, the ECS service will automatically launch replacement tasks in the remaining healthy AZs to maintain the desired count, ensuring continued traffic serving without manual intervention.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A financial services company runs a critical application on Amazon ECS with Fargate launch type. The application has strict availability requirements and must survive an Availability Zone failure. The ECS service is configured with a desired count of 4 tasks, spread across two Availability Zones using a spread strategy. The service is fronted by an Application Load Balancer. During a recent AZ outage, one AZ became completely unavailable, but the application continued to serve traffic. However, after the AZ recovered, the ECS service did not automatically place new tasks in the recovered AZ to restore the desired count. The service remains with only 2 tasks in the remaining AZ. What is the most likely cause and solution?
hard
✓ A.The ECS service does not automatically replace tasks in a recovered AZ because the spread strategy is static. Manually update the service (e.g., force new deployment) to trigger rebalancing.
B.The Application Load Balancer is not health-checking the recovered AZ. Configure cross-zone load balancing.
C.The ECS service uses a spread strategy that does not automatically rebalance after an AZ recovers. Update the service to use a 'rebalance' strategy.
D.The ECS service is configured with a minimum healthy percent of 50%, which prevents replacement. Lower the minimum healthy percent to 0%.
Why A: The ECS service uses a spread strategy, which maintains balance across AZs. When an AZ is unhealthy, ECS does not place tasks there. After recovery, the service may not automatically rebalance because the spread strategy is not proactive; it only ensures placement of new tasks. To force rebalancing, one can update the service (e.g., change desired count, then change back).
Last reviewed: Jun 24, 2026
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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.
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