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 uses Amazon CloudFront to serve static content from an S3 bucket. Users in a specific region report slow load times. The DevOps team checks CloudFront metrics and sees a high error rate (5xx) for that region. The S3 bucket is healthy. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The S3 bucket policy does not grant access to the CloudFront origin access identity (OAI).
A high 5xx error rate from CloudFront combined with a healthy S3 bucket strongly indicates that CloudFront cannot fetch objects from the origin. If the S3 bucket policy does not grant access to the CloudFront origin access identity (OAI), CloudFront receives an access denied (403) response from S3, which CloudFront translates into a 5xx error for the user. This is the most common cause of regional 5xx errors when the origin is otherwise healthy.
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.
✗
The AWS WAF web ACL is blocking requests from that region.
Why it's wrong here
WAF blocking returns 403, not 5xx.
✓
The S3 bucket policy does not grant access to the CloudFront origin access identity (OAI).
Why this is correct
Misconfigured OAI causes 403 errors that may appear as 5xx if not handled properly.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The CloudFront distribution's default TTL is too short.
Why it's wrong here
Short TTL might cause more origin requests but not 5xx errors.
✗
The CloudFront origin shield is misconfigured.
Why it's wrong here
Origin shield is optional and would not cause 5xx errors if origin is healthy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume 5xx errors always indicate an origin server problem, but in CloudFront, a 5xx can also result from an authentication failure (403) at the origin, which CloudFront converts to a 5xx for the viewer.
Detailed technical explanation
How to think about this question
CloudFront uses an Origin Access Identity (OAI) to authenticate requests to S3. When the S3 bucket policy explicitly denies access to the OAI (or does not grant it), S3 returns a 403 AccessDenied error. CloudFront treats this as an origin error and, depending on the error caching configuration, may return a 502 or 503 status to the client. This scenario is common when the bucket policy is misconfigured after a distribution update or when the OAI is accidentally removed from the policy.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The S3 bucket policy does not grant access to the CloudFront origin access identity (OAI). — A high 5xx error rate from CloudFront combined with a healthy S3 bucket strongly indicates that CloudFront cannot fetch objects from the origin. If the S3 bucket policy does not grant access to the CloudFront origin access identity (OAI), CloudFront receives an access denied (403) response from S3, which CloudFront translates into a 5xx error for the user. This is the most common cause of regional 5xx errors when the origin is otherwise healthy.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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