The correct answer is to create an origin access identity (OAI) in CloudFront and update the S3 bucket policy to allow only the OAI to read objects. This works because the OAI acts as a special CloudFront user that authenticates requests to the S3 origin; by configuring the bucket policy to grant GetObject permissions exclusively to that OAI’s ARN, any direct request to the S3 endpoint without CloudFront’s signature is denied, effectively restricting S3 bucket access to CloudFront only. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of securing static content delivery and avoiding common misconfigurations like leaving a bucket publicly readable—a frequent trap where candidates mistakenly suggest using a pre-signed URL or bucket ACLs instead of the OAI-based policy. Remember the memory tip: “OAI locks the door, only CloudFront holds the key.”
DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 static website on Amazon S3 with public read access. The website content is stored in an S3 bucket and served through an Amazon CloudFront distribution for better performance and security. Recently, the company noticed that some users are accessing the S3 bucket directly via the S3 endpoint, bypassing CloudFront. This increases costs and exposes the bucket to potential attacks. The company wants to ensure that all access to the website goes through CloudFront only. Which solution should the company implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an origin access identity (OAI) in CloudFront and update the S3 bucket policy to allow only the OAI to read objects.
To restrict access to the S3 bucket only through CloudFront, use an origin access identity (OAI) and a bucket policy that allows only the OAI. This way, direct access via S3 URL is denied.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Set the S3 bucket policy to deny all requests that do not come from the CloudFront distribution's IP addresses.
Why it's wrong here
CloudFront IP addresses can change; using OAI is more reliable.
✗
Configure the S3 bucket to use AWS WAF to block requests that do not have a custom header set by CloudFront.
Why it's wrong here
WAF cannot block direct S3 access because S3 does not support WAF.
✓
Create an origin access identity (OAI) in CloudFront and update the S3 bucket policy to allow only the OAI to read objects.
Why this is correct
OAI ensures only CloudFront can access the bucket.
Related concept
Standard ACLs match source addresses.
✗
Change the S3 bucket to be private and use presigned URLs for all requests.
Why it's wrong here
Presigned URLs would require application changes and not force CloudFront usage.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DOP-C02 ACL questions on filtering logic and placement.
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Create an origin access identity (OAI) in CloudFront and update the S3 bucket policy to allow only the OAI to read objects. — To restrict access to the S3 bucket only through CloudFront, use an origin access identity (OAI) and a bucket policy that allows only the OAI. This way, direct access via S3 URL is denied.
What should I do if I get this DOP-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DOP-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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