- A
Configure an RDS read replica in a different Availability Zone.
Why wrong: Read replicas are not automatically promoted for failover; Multi-AZ is the correct approach.
- B
Use a Single-AZ RDS for MySQL database to keep costs low.
Why wrong: Single-AZ does not provide automatic failover if the AZ fails.
- C
Place all EC2 instances in the same Availability Zone to reduce cross-AZ data transfer costs.
Why wrong: This creates a single point of failure for the web tier.
- D
Configure the Auto Scaling group to launch EC2 instances in at least two Availability Zones.
Distributing instances across AZs provides high availability for the web tier.
- E
Deploy the RDS for MySQL database in a Multi-AZ configuration.
Multi-AZ provides automatic failover to a standby in a different AZ.
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 is building a multi-tier web application on AWS. The application must be resilient to the failure of an entire Availability Zone. The architecture includes an Application Load Balancer (ALB), EC2 instances in an Auto Scaling group, and an Amazon RDS for MySQL database. Which TWO actions should be taken to achieve this resilience? (Choose two.)
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
Configure the Auto Scaling group to launch EC2 instances in at least two Availability Zones.
Option D is correct because configuring the Auto Scaling group to launch EC2 instances in at least two Availability Zones ensures that if one AZ fails, the remaining AZ(s) can continue serving traffic. This is a fundamental pattern for building AZ-resilient compute tiers. Option E is correct because deploying Amazon RDS for MySQL in a Multi-AZ configuration automatically provisions and maintains a synchronous standby replica in a different AZ, providing automatic failover if the primary DB instance fails, thus ensuring database resilience.
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.
- ✗
Configure an RDS read replica in a different Availability Zone.
Why it's wrong here
Read replicas are not automatically promoted for failover; Multi-AZ is the correct approach.
- ✗
Use a Single-AZ RDS for MySQL database to keep costs low.
Why it's wrong here
Single-AZ does not provide automatic failover if the AZ fails.
- ✗
Place all EC2 instances in the same Availability Zone to reduce cross-AZ data transfer costs.
Why it's wrong here
This creates a single point of failure for the web tier.
- ✓
Configure the Auto Scaling group to launch EC2 instances in at least two Availability Zones.
Why this is correct
Distributing instances across AZs provides high availability for the web tier.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Deploy the RDS for MySQL database in a Multi-AZ configuration.
Why this is correct
Multi-AZ provides automatic failover to a standby in a different AZ.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse read replicas (asynchronous, for read scaling) with Multi-AZ deployments (synchronous, for high availability), and mistakenly think placing all resources in one AZ reduces costs without recognizing the critical single point of failure it introduces.
Detailed technical explanation
How to think about this question
Multi-AZ RDS for MySQL uses synchronous replication to a standby instance in a different AZ, with automatic failover typically completing within 60-120 seconds. The Auto Scaling group distributes EC2 instances across AZs based on the subnets specified in the launch template or configuration, and the ALB automatically routes traffic only to healthy instances in remaining AZs during a failure. This combination ensures that both compute and database tiers can survive an entire AZ outage 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
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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
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 Auto Scaling group to launch EC2 instances in at least two Availability Zones. — Option D is correct because configuring the Auto Scaling group to launch EC2 instances in at least two Availability Zones ensures that if one AZ fails, the remaining AZ(s) can continue serving traffic. This is a fundamental pattern for building AZ-resilient compute tiers. Option E is correct because deploying Amazon RDS for MySQL in a Multi-AZ configuration automatically provisions and maintains a synchronous standby replica in a different AZ, providing automatic failover if the primary DB instance fails, thus ensuring database resilience.
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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Last reviewed: Jun 11, 2026
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