The answer is to configure the Auto Scaling group to launch instances in multiple Availability Zones and to place an Application Load Balancer in front of those instances. This combination ensures high availability across multiple AZs because if one AZ fails, the Auto Scaling group automatically maintains capacity in the remaining zones, while the ALB distributes incoming traffic only to healthy targets across those zones. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of fault-tolerant architecture patterns—specifically that cross-zone load balancing with an ALB is required, not a single-AZ setup or a Classic Load Balancer. A common trap is assuming a single AZ with more instances is sufficient, but true high availability demands geographic redundancy. Memory tip: think “Spread and Balance”—spread instances across AZs, then balance traffic with an ALB.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. 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 EC2 instances in an Auto Scaling group. The application must be highly available across multiple Availability Zones. Which TWO configurations are necessary to achieve this? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place an Application Load Balancer in front of the Auto Scaling group.
Options A and D are correct. Option A: Distributing instances across multiple AZs ensures that if one AZ fails, the application continues in other AZs. Option D: An Application Load Balancer (ALB) distributes traffic across instances in multiple AZs. Option B is wrong because a single AZ defeats high availability. Option C is wrong because a Classic Load Balancer is not recommended; ALB is better for cross-zone. Option E is wrong because spot instances can be terminated, reducing availability.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 single Availability Zone to reduce latency.
Why it's wrong here
Single AZ is a single point of failure.
✗
Use Spot Instances to reduce costs.
Why it's wrong here
Spot instances can be interrupted, compromising availability.
✗
Use a Classic Load Balancer to distribute traffic.
Why it's wrong here
CLB does not support cross-zone load balancing without additional configuration.
✓
Place an Application Load Balancer in front of the Auto Scaling group.
Why this is correct
ALB distributes traffic across AZs and instances.
Related concept
Static NAT maps one inside address to one outside address.
✓
Configure the Auto Scaling group to launch instances in multiple Availability Zones.
Why this is correct
Multiple AZs provide fault tolerance.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
Incident and Event Response — This question tests Incident and Event Response — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Place an Application Load Balancer in front of the Auto Scaling group. — Options A and D are correct. Option A: Distributing instances across multiple AZs ensures that if one AZ fails, the application continues in other AZs. Option D: An Application Load Balancer (ALB) distributes traffic across instances in multiple AZs. Option B is wrong because a single AZ defeats high availability. Option C is wrong because a Classic Load Balancer is not recommended; ALB is better for cross-zone. Option E is wrong because spot instances can be terminated, reducing availability.
What should I do if I get this DOP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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