The answer is to apply an S3 bucket policy that denies s3:PutObject unless the required encryption headers are present. This works because the policy uses a condition key like s3:x-amz-server-side-encryption-aws:kms to enforce that every upload includes the x-amz-server-side-encryption header specifying the customer-managed KMS key, rejecting any request that lacks it. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of preventive controls versus detective controls—many candidates mistakenly choose default encryption or bucket settings, but those only apply when the client omits headers, not when a user actively bypasses encryption. The trap is that bucket policies are evaluated before the upload, making them the only way to block unencrypted objects at the point of write, regardless of the IAM principal or tool used. Memory tip: “Deny before default”—a bucket policy with a deny condition on PutObject is the only way to enforce encryption proactively, not reactively.
SAP-C02 Practice Question: Design Solutions for Organizational Complexity
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. 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 has a data lake in AWS using S3 and Glue. The security team requires that all data in the data lake be encrypted at rest using a customer-managed KMS key. However, some users are able to upload data without encryption. What is the most effective way to enforce encryption?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Apply an S3 bucket policy that denies s3:PutObject unless encryption headers are present
Option A is correct because an S3 bucket policy with a condition that denies s3:PutObject unless the x-amz-server-side-encryption header is present and specifies the required KMS key enforces encryption at the point of upload. This prevents any unencrypted object from being written to the bucket, regardless of the client or tool used, and works with any IAM principal. It is the most effective and direct method to enforce encryption for all uploads.
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.
✓
Apply an S3 bucket policy that denies s3:PutObject unless encryption headers are present
Why this is correct
Bucket policies can enforce encryption at upload time.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use AWS Config rules to remediate non-compliant objects
Why it's wrong here
Remediation is reactive, not preventive.
✗
Require users to use pre-signed URLs for uploads
Why it's wrong here
Pre-signed URLs do not enforce encryption.
✗
Attach an SCP that denies s3:PutObject without encryption
Why it's wrong here
SCPs are account-level, not bucket-level.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose AWS Config (Option B) thinking it can enforce encryption, but Config is detective and reactive, not preventive, whereas a bucket policy with a deny condition is the only way to block unencrypted uploads at the API level.
Detailed technical explanation
How to think about this question
The bucket policy condition key s3:x-amz-server-side-encryption checks for the presence of the encryption header in the request, and you can further restrict to a specific KMS key using kms:EncryptionContext or by validating the key ARN in the policy. Under the hood, S3 evaluates the bucket policy before processing the PutObject request, so a deny on missing encryption headers results in an AccessDenied error, preventing the object from being written. In a real-world scenario, this approach also works with multipart uploads, as each part must include the encryption header to comply with 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.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Apply an S3 bucket policy that denies s3:PutObject unless encryption headers are present — Option A is correct because an S3 bucket policy with a condition that denies s3:PutObject unless the x-amz-server-side-encryption header is present and specifies the required KMS key enforces encryption at the point of upload. This prevents any unencrypted object from being written to the bucket, regardless of the client or tool used, and works with any IAM principal. It is the most effective and direct method to enforce encryption for all uploads.
What should I do if I get this SAP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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