The answer is to terminate unhealthy instances via the Auto Scaling group, configure health checks on the ALB, and set up Amazon SNS notifications for Auto Scaling events. This trio automates the response to EC2 instance failure by ensuring the Auto Scaling group detects the failure through the ALB health checks, immediately terminates the unhealthy instance, and launches a replacement, while SNS alerts the operations team. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding that Auto Scaling, not CloudWatch or scaling policies, handles individual instance recovery—a common trap is confusing scaling policies (which adjust fleet size) with instance-level health checks. Remember the memory tip: “ALB checks, ASG terminates, SNS alerts”—these three steps form the complete automation loop for instance failure response.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 behind an Application Load Balancer (ALB) in an Auto Scaling group. The team wants to automate the response to an instance failure. Which THREE steps should be taken to ensure automatic recovery and notification?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure Auto Scaling to replace unhealthy instances
Option A is correct to terminate unhealthy instances. Option C is correct to send notifications via SNS. Option D is correct to configure health checks on ALB. Option B is wrong because scaling policies adjust capacity but do not handle individual instance failures. Option E is wrong because CloudWatch can terminate instances but Auto Scaling handles it.
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.
✗
Create a CloudWatch alarm to terminate the instance
Why it's wrong here
Auto Scaling already handles termination; direct termination may cause issues.
✓
Configure Auto Scaling to replace unhealthy instances
Why this is correct
Auto Scaling can automatically terminate and launch instances based on health checks.
Related concept
Static NAT maps one inside address to one outside address.
✓
Configure the ALB health check to mark instances as unhealthy
Why this is correct
ALB health checks are used by Auto Scaling to determine instance health.
Related concept
Static NAT maps one inside address to one outside address.
✓
Set up Amazon SNS notifications for Auto Scaling events
Why this is correct
SNS can notify the team when instances are terminated.
Related concept
Static NAT maps one inside address to one outside address.
✗
Create a scaling policy based on CPU utilization
Why it's wrong here
Scaling policies adjust capacity but do not replace failed instances.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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: Configure Auto Scaling to replace unhealthy instances — Option A is correct to terminate unhealthy instances. Option C is correct to send notifications via SNS. Option D is correct to configure health checks on ALB. Option B is wrong because scaling policies adjust capacity but do not handle individual instance failures. Option E is wrong because CloudWatch can terminate instances but Auto Scaling handles it.
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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