The answer is to review AWS CloudTrail logs for TerminateInstances API calls. This is the correct first step because CloudTrail records every API action taken within an AWS account, capturing the source IP, user agent, and identity that issued the termination request, which is essential for root cause analysis when an EC2 instance disappears unexpectedly. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your incident response workflow and understanding that CloudTrail is the authoritative source for investigating any resource lifecycle event, especially when an Auto Scaling group is involved—a common trap is diving into application logs or scaling policies first, but those won’t reveal who or what triggered the termination. Memory tip: think “CT first” for “CloudTrail Termination”—always check the API trail before blaming the app or the group.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. 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 DevOps engineer notices that an EC2 instance running a critical web application has been terminated unexpectedly. The instance was part of an Auto Scaling group. Which step should the engineer take FIRST to investigate the root cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Review AWS CloudTrail logs for TerminateInstances API calls.
Option A is correct because the first step in incident response is to gather information. CloudTrail logs all API calls, including TerminateInstances, and can identify who or what terminated the instance. Option B is wrong because examining the application logs does not reveal the termination cause. Option C is wrong because scaling policies would not cause termination without CloudWatch. Option D is wrong because the termination reason is not available in the console without checking logs.
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.
✓
Review AWS CloudTrail logs for TerminateInstances API calls.
Why this is correct
CloudTrail logs all API calls and can identify the source of termination.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Look at the EC2 console's 'Termination Protection' setting.
Why it's wrong here
Termination protection does not log the reason for termination.
✗
Check the application logs on the instance's attached EBS volume (detached and attached to another instance).
Why it's wrong here
Application logs do not show termination reasons.
✗
Verify the Auto Scaling group's scaling policies and scheduled actions.
Why it's wrong here
Scaling policies do not cause termination without CloudWatch alarms.
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.
Trap categories for this question
Command / output trap
Application logs do not show termination reasons.
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: Review AWS CloudTrail logs for TerminateInstances API calls. — Option A is correct because the first step in incident response is to gather information. CloudTrail logs all API calls, including TerminateInstances, and can identify who or what terminated the instance. Option B is wrong because examining the application logs does not reveal the termination cause. Option C is wrong because scaling policies would not cause termination without CloudWatch. Option D is wrong because the termination reason is not available in the console without checking logs.
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.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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