The answer is that the objects are encrypted with SSE-C (server-side encryption with customer-provided keys). CloudFront Origin Access Control (OAC) cannot decrypt objects encrypted with SSE-C because CloudFront does not have access to the customer-provided encryption key; the key must be supplied with each GET request, which CloudFront cannot do when fetching from an origin. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how CloudFront interacts with different S3 encryption types—SSE-S3 and SSE-KMS work seamlessly with OAC, but SSE-C always causes a 403 Forbidden error because the service cannot retrieve the object without the key. A common trap is to blame the bucket policy or OAC configuration, but the real issue is the encryption mismatch. Memory tip: "C in SSE-C stands for Customer key, and CloudFront Can't Crack it."
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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 developer is using Amazon CloudFront to distribute content from an S3 bucket. The bucket is configured as an origin with Origin Access Control (OAC). Recently, some users have reported that they receive 403 Forbidden errors when accessing certain objects. The developer checks the CloudFront distribution and confirms that the OAC is set up correctly. The S3 bucket policy allows the CloudFront service principal to get objects. The developer also notes that the objects in question have been updated recently. What is the MOST likely cause of the 403 errors?
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 objects are encrypted with SSE-C (server-side encryption with customer-provided keys).
Option D is correct because CloudFront may be serving cached stale objects from edge locations. If the object is updated but the cache TTL has not expired, CloudFront serves the old object. However, the question says users receive 403 errors, not old content. Actually, 403 errors could occur if the object permissions changed. But more likely, the issue is that the new objects have different permissions or the bucket policy does not cover the new objects' paths. Option A is wrong because OAC is correctly configured. Option B is wrong because the CloudFront origin is not a website endpoint. Option C is wrong because the bucket policy allows access. The most plausible cause is that the objects were updated and the S3 bucket policy has a condition that restricts access based on a header that the new objects do not have. But given typical scenarios, the correct answer is often that the objects are not publicly accessible? However, with OAC, objects do not need to be public. Actually, if the objects were uploaded with a bucket policy that denies access to everyone except CloudFront, but the objects were uploaded with a different owner? Wait. The correct answer is likely D: The objects were uploaded with a different AWS account? No. Let's think: The most common cause is that the object's permissions were set to private and the bucket policy only grants access to CloudFront, but if the object is owned by a different account, the bucket policy might not apply. However, that is complex. A simpler explanation: The objects were updated and the bucket policy includes a condition that requires a specific header that the new objects' requests do not have. But the question says the objects in question have been updated recently. The best answer is that the objects were updated with a different encryption key? Actually, the correct answer is: The objects were uploaded with SSE-C (customer-provided encryption keys) and CloudFront cannot access them because it does not have the encryption key. Option A: The OAC configuration is incorrect. Option B: The CloudFront distribution is using the S3 website endpoint. Option C: The bucket policy denies access to the CloudFront service principal. Option D: The objects are encrypted with SSE-C. That is a known issue: CloudFront cannot serve objects encrypted with SSE-C. So Option D is correct.
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.
✓
The objects are encrypted with SSE-C (server-side encryption with customer-provided keys).
Why this is correct
CloudFront cannot decrypt objects encrypted with SSE-C, resulting in 403 errors.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The OAC configuration is not correctly associated with the CloudFront distribution.
Why it's wrong here
The developer confirmed OAC is set up correctly.
✗
The S3 bucket policy denies access to the CloudFront service principal.
Why it's wrong here
The bucket policy allows access.
✗
The CloudFront distribution is configured to use the S3 website endpoint instead of the REST endpoint.
Why it's wrong here
Using the website endpoint would not cause 403 with OAC.
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 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.
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 DVA-C02 NAT questions on configuration and troubleshooting.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The objects are encrypted with SSE-C (server-side encryption with customer-provided keys). — Option D is correct because CloudFront may be serving cached stale objects from edge locations. If the object is updated but the cache TTL has not expired, CloudFront serves the old object. However, the question says users receive 403 errors, not old content. Actually, 403 errors could occur if the object permissions changed. But more likely, the issue is that the new objects have different permissions or the bucket policy does not cover the new objects' paths. Option A is wrong because OAC is correctly configured. Option B is wrong because the CloudFront origin is not a website endpoint. Option C is wrong because the bucket policy allows access. The most plausible cause is that the objects were updated and the S3 bucket policy has a condition that restricts access based on a header that the new objects do not have. But given typical scenarios, the correct answer is often that the objects are not publicly accessible? However, with OAC, objects do not need to be public. Actually, if the objects were uploaded with a bucket policy that denies access to everyone except CloudFront, but the objects were uploaded with a different owner? Wait. The correct answer is likely D: The objects were uploaded with a different AWS account? No. Let's think: The most common cause is that the object's permissions were set to private and the bucket policy only grants access to CloudFront, but if the object is owned by a different account, the bucket policy might not apply. However, that is complex. A simpler explanation: The objects were updated and the bucket policy includes a condition that requires a specific header that the new objects' requests do not have. But the question says the objects in question have been updated recently. The best answer is that the objects were updated with a different encryption key? Actually, the correct answer is: The objects were uploaded with SSE-C (customer-provided encryption keys) and CloudFront cannot access them because it does not have the encryption key. Option A: The OAC configuration is incorrect. Option B: The CloudFront distribution is using the S3 website endpoint. Option C: The bucket policy denies access to the CloudFront service principal. Option D: The objects are encrypted with SSE-C. That is a known issue: CloudFront cannot serve objects encrypted with SSE-C. So Option D is correct.
What should I do if I get this DVA-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 DVA-C02 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.