DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 uses Amazon Route 53 for DNS and wants to ensure high availability for a web application hosted on two EC2 instances in different Availability Zones. The application uses an Application Load Balancer. What is the simplest way to achieve resilience if one Availability Zone becomes unavailable?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place the instances in different Availability Zones behind the ALB.
Option B is correct because placing EC2 instances in different Availability Zones behind an Application Load Balancer (ALB) is the simplest and most effective way to achieve high availability. The ALB automatically distributes traffic across healthy targets in multiple AZs, and if one AZ becomes unavailable, the ALB stops routing requests to instances in that AZ, ensuring continued service from the remaining AZ.
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.
✗
Launch both instances in the same Availability Zone.
Why it's wrong here
Same AZ does not protect against AZ failure.
✓
Place the instances in different Availability Zones behind the ALB.
Why this is correct
ALB automatically distributes traffic and detects health, providing resilience.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure Route 53 latency-based routing to each instance.
Why it's wrong here
Latency routing does not consider health.
✗
Configure Route 53 failover routing with health checks pointing to each instance.
Why it's wrong here
ALB already provides health checks and cross-AZ routing; Route 53 failover is unnecessary.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates overcomplicate the solution by choosing DNS-level failover (Option D) when the ALB already provides built-in cross-AZ failover, making the simpler architecture the correct answer.
Detailed technical explanation
How to think about this question
The ALB operates at the application layer (Layer 7) and maintains a target group that includes instances from multiple AZs. When an AZ fails, the ALB's health checks detect the unhealthy targets and automatically stop sending traffic to them, typically within 30 seconds (three consecutive failed health checks at 10-second intervals). This is more efficient than DNS-based failover, which can be delayed by TTL caching (often 60 seconds or more) and requires additional Route 53 configuration.
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: Place the instances in different Availability Zones behind the ALB. — Option B is correct because placing EC2 instances in different Availability Zones behind an Application Load Balancer (ALB) is the simplest and most effective way to achieve high availability. The ALB automatically distributes traffic across healthy targets in multiple AZs, and if one AZ becomes unavailable, the ALB stops routing requests to instances in that AZ, ensuring continued service from the remaining AZ.
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.
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Question Discussion
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