The answer is to add an S3 bucket policy that denies s3:PutObject unless the request includes the x-amz-server-side-encryption header. This approach enforces encryption at rest by rejecting any upload that lacks the required encryption header, regardless of how the bucket was created—including via CloudFormation. The policy condition uses a Deny effect with a StringNotEquals condition on s3:x-amz-server-side-encryption, ensuring that every object written to the bucket must specify encryption, which directly addresses the security team’s requirement. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of policy-based controls over infrastructure-as-code defaults, as many candidates mistakenly try to enforce encryption solely through CloudFormation bucket properties, which can be overridden by later uploads. A common trap is assuming that setting DefaultEncryption on the bucket is sufficient, but a bucket policy is the only way to guarantee compliance for all PutObject operations. Memory tip: “Deny the upload if the header is missing—policy beats property every time.”
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing 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 is using AWS CloudFormation to deploy infrastructure. The security team requires that all Amazon S3 buckets created by CloudFormation must be encrypted at rest. What should a solutions architect do to enforce this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add an S3 bucket policy that denies s3:PutObject without the x-amz-server-side-encryption header.
Option B is correct because an S3 bucket policy that denies s3:PutObject unless the request includes the x-amz-server-side-encryption header enforces encryption at rest for all objects uploaded to the bucket. This policy condition works regardless of how the bucket is created, including via CloudFormation, and ensures that any PutObject operation without the required encryption header is rejected, meeting the security team's requirement.
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.
✗
Enable default encryption on each bucket using SSE-S3.
Why it's wrong here
Default encryption only applies to objects uploaded without encryption headers; it can be overridden.
✓
Add an S3 bucket policy that denies s3:PutObject without the x-amz-server-side-encryption header.
Why this is correct
The bucket policy rejects unencrypted uploads.
Related concept
Read the scenario before looking for a memorised answer.
✗
Require that all buckets use AWS KMS managed keys for encryption.
Why it's wrong here
This does not enforce encryption at upload time.
✗
Use a CloudFormation stack policy to prevent modification of bucket encryption settings.
Why it's wrong here
Stack policies protect resources from updates, not from unencrypted uploads.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse default encryption (which passively encrypts objects but does not enforce encryption) with a bucket policy that actively denies unencrypted uploads, leading them to choose Option A instead of the correct enforcement mechanism.
Detailed technical explanation
How to think about this question
The x-amz-server-side-encryption header can be set to AES256 (SSE-S3) or aws:kms (SSE-KMS). The bucket policy condition aws:SourceArn can be used to restrict the policy to specific CloudFormation stacks, ensuring only compliant deployments are allowed. In practice, this policy must be applied to each bucket individually or via a service control policy (SCP) at the organizational level for broader enforcement.
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.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add an S3 bucket policy that denies s3:PutObject without the x-amz-server-side-encryption header. — Option B is correct because an S3 bucket policy that denies s3:PutObject unless the request includes the x-amz-server-side-encryption header enforces encryption at rest for all objects uploaded to the bucket. This policy condition works regardless of how the bucket is created, including via CloudFormation, and ensures that any PutObject operation without the required encryption header is rejected, meeting the security team's requirement.
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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