The correct answer is to deny PutObject requests where the x-amz-server-side-encryption header is not set to aws:kms. This bucket policy statement enforces SSE-KMS encryption by explicitly rejecting any upload that fails to include the required encryption header, ensuring all objects written to the S3 bucket are automatically encrypted at rest with AWS KMS. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how bucket policies can mandate encryption settings at the request level, rather than relying on default bucket encryption settings alone—a common trap is confusing default encryption with policy-based enforcement. Remember that default encryption applies only when no header is provided, while a Deny policy forces the client to explicitly set the header. Memory tip: think “Deny the missing header” to enforce SSE-KMS.
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. 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 data engineer is designing a data lake on Amazon S3 and needs to ensure that objects are automatically encrypted at rest using server-side encryption with AWS KMS. Which bucket policy statement achieves this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deny PutObject requests where the x-amz-server-side-encryption header is not set to aws:kms.
Option A is correct because it enforces server-side encryption with AWS KMS (SSE-KMS) by denying any PutObject request that does not include the `x-amz-server-side-encryption` header set to `aws:kms`. This bucket policy ensures that all objects written to the S3 bucket are automatically encrypted at rest using AWS KMS, meeting the requirement for mandatory encryption with a specific key management service.
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.
✓
Deny PutObject requests where the x-amz-server-side-encryption header is not set to aws:kms.
Why this is correct
Enforces SSE-KMS encryption.
Related concept
Read the scenario before looking for a memorised answer.
✗
Deny PutObject requests that do not include the x-amz-server-side-encryption header.
Why it's wrong here
Does not enforce KMS specifically.
✗
Deny PutObject requests where the x-amz-server-side-encryption header is not set to AES256.
Why it's wrong here
This enforces SSE-S3, not KMS.
✗
Allow PutObject requests only if the x-amz-server-side-encryption header is set to AES256.
Why it's wrong here
This enforces SSE-S3, not KMS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the encryption header values (`aws:kms` vs `AES256`) and mistakenly choose an option that enforces SSE-S3 (AES256) instead of SSE-KMS, or they pick a Deny statement that only checks for the presence of the header without validating its specific value.
Detailed technical explanation
How to think about this question
Under the hood, S3 bucket policies are evaluated before the request is processed, and the `s3:x-amz-server-side-encryption` condition key checks the value of the `x-amz-server-side-encryption` header in the request. When using SSE-KMS, the header value must be `aws:kms`, and the bucket policy can also optionally require a specific KMS key via the `s3:x-amz-server-side-encryption-aws-kms-key-id` condition key. A real-world scenario where this matters is in regulated industries where audit trails require that all data is encrypted with a customer-managed KMS key, and the bucket policy ensures compliance even if a client forgets to set the encryption header.
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.
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deny PutObject requests where the x-amz-server-side-encryption header is not set to aws:kms. — Option A is correct because it enforces server-side encryption with AWS KMS (SSE-KMS) by denying any PutObject request that does not include the `x-amz-server-side-encryption` header set to `aws:kms`. This bucket policy ensures that all objects written to the S3 bucket are automatically encrypted at rest using AWS KMS, meeting the requirement for mandatory encryption with a specific key management service.
What should I do if I get this DEA-C01 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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