The answer is deploying EC2 instances across two Availability Zones and configuring the Application Load Balancer to distribute traffic. This solution is most resilient and cost-effective because it eliminates the single point of failure by placing instances in physically separate data centers, while the ALB automatically routes traffic away from a failed zone without requiring over-provisioned standby capacity. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how Multi-AZ architectures with Auto Scaling groups achieve high availability without unnecessary expense—a common trap is choosing to add more instances in one zone or using a multi-region setup, which either fails to address zone failure or introduces excessive cost and complexity. Remember, resilience is about distribution, not duplication: spreading across zones beats stacking in one. A useful memory tip is “two zones, one ALB, no single point of grief.”
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 web application on EC2 instances behind an Application Load Balancer. The application experiences intermittent failures due to a single Availability Zone failing. Which solution is MOST resilient and cost-effective?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy EC2 instances across two Availability Zones and configure the ALB to distribute traffic
Option B is correct because distributing instances across multiple Availability Zones ensures high availability without over-provisioning. Option A is wrong because it only adds capacity in one zone. Option C is wrong because it is more expensive and complex. Option D is wrong because it does not address availability zone failure.
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 a larger instance type in the same Availability Zone
Why it's wrong here
Does not provide multi-AZ resilience.
✗
Use an Auto Scaling group with a single instance in each of three Availability Zones and a Network Load Balancer
Why it's wrong here
Overkill and more expensive; ALB is sufficient.
✗
Migrate to a single larger instance in a different region
Why it's wrong here
Not cost-effective and adds latency.
✓
Deploy EC2 instances across two Availability Zones and configure the ALB to distribute traffic
Why this is correct
Provides fault isolation and load balancing across zones.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Deploy EC2 instances across two Availability Zones and configure the ALB to distribute traffic — Option B is correct because distributing instances across multiple Availability Zones ensures high availability without over-provisioning. Option A is wrong because it only adds capacity in one zone. Option C is wrong because it is more expensive and complex. Option D is wrong because it does not address availability zone failure.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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 startup runs a web application on EC2 instances behind an Application Load Balancer. They want to improve resilience by distributing instances across multiple Availability Zones. Currently, all instances are in us-east-1a. They create a launch template and an Auto Scaling group with a desired capacity of 2. They configure the Auto Scaling group to use two subnets: one in us-east-1a and one in us-east-1b. However, after updating, all instances remain in us-east-1a. What is the most likely reason?
easy
A.The instance type is not available in us-east-1b.
✓ B.The Auto Scaling group's subnet configuration was not updated to include the new subnet.
C.The new subnet in us-east-1b has no route to the internet.
D.The launch template specifies a single subnet in us-east-1a.
Why B: Auto Scaling group distributes instances across subnets specified. If only one subnet is used, it may be because the launch template specifies only one subnet or the Auto Scaling group's subnets were not updated. The most common cause is that the Auto Scaling group's subnet list still contains only the original subnet.
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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.
Question Discussion
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