The answer is that the KMS key policy for the CMK used for S3 encryption does not grant the GlueETLRole permission to use the key. Even though the IAM role has the required kms:Decrypt and kms:GenerateDataKey permissions attached, AWS KMS requires that the key’s resource-based policy explicitly allow the principal—here, the GlueETLRole—to call those actions. When the S3 bucket uses SSE-KMS, every GET request triggers a kms:Decrypt call, and without the key policy granting that permission, the request fails with an Access Denied error. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding that KMS permissions are a two-way gate: IAM policies and key policies must both grant access, and the key policy is often the overlooked culprit. A common trap is assuming IAM permissions alone suffice, but the key policy acts as the final authorization layer. Memory tip: “IAM says you can, but the key policy says you may”—always check the key policy when SSE-KMS access fails.
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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 healthcare company stores patient records in an S3 bucket encrypted with SSE-S3. The data engineering team uses AWS Glue ETL jobs to process this data and load it into an Amazon Redshift cluster for analytics. Recently, the security team mandated that all sensitive data must be encrypted at rest using customer-managed keys (CMK) in AWS KMS, and that the keys must be rotated automatically every year. The team updated the S3 bucket to use SSE-KMS with a CMK and enabled automatic key rotation. However, after the change, the Glue ETL jobs that read from the S3 bucket started failing with 'Access Denied' errors. The Glue job uses an IAM role named 'GlueETLRole' that has the following permissions: s3:GetObject on the bucket, kms:Decrypt and kms:GenerateDataKey on the CMK, and all necessary Glue permissions. The Redshift cluster is also encrypted with a different CMK, and the Glue role has kms:Decrypt on that key as well. What is the most likely cause of the failure?
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 KMS key policy for the CMK used for S3 encryption does not grant 'GlueETLRole' permission to use the key.
Option B is correct. When using SSE-KMS, the Glue job needs to call kms:Decrypt to decrypt the data, but the S3 GET request also requires kms:Decrypt permission. The role has kms:Decrypt, but the key policy of the CMK must also grant the role permission. Option A is wrong because the role has the required KMS permissions. Option C is wrong because Glue does not need kms:Encrypt for reading. Option D is wrong because VPC endpoint policy may block but is less likely.
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 KMS key policy for the CMK used for S3 encryption does not grant 'GlueETLRole' permission to use the key.
Why this is correct
The key policy must allow the IAM role to use the key.
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 IAM role 'GlueETLRole' does not have kms:Decrypt permission on the CMK used for S3 encryption.
Why it's wrong here
The role does have kms:Decrypt permission as stated.
✗
The Glue job requires kms:Encrypt permission to read encrypted data from S3.
Why it's wrong here
Reading requires kms:Decrypt, not Encrypt.
✗
The S3 VPC endpoint policy does not allow the Glue job to access the KMS key.
Why it's wrong here
VPC endpoint policy could be a factor, but the key policy is more direct.
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 DEA-C01 NAT questions on configuration and troubleshooting.
Data Security and Governance — This question tests Data Security and Governance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The KMS key policy for the CMK used for S3 encryption does not grant 'GlueETLRole' permission to use the key. — Option B is correct. When using SSE-KMS, the Glue job needs to call kms:Decrypt to decrypt the data, but the S3 GET request also requires kms:Decrypt permission. The role has kms:Decrypt, but the key policy of the CMK must also grant the role permission. Option A is wrong because the role has the required KMS permissions. Option C is wrong because Glue does not need kms:Encrypt for reading. Option D is wrong because VPC endpoint policy may block but is less likely.
What should I do if I get this DEA-C01 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 DEA-C01 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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company stores sensitive customer data in an S3 bucket. The security team requires that all data be encrypted at rest using a customer-managed AWS KMS key. However, when a data engineer attempts to upload an object using the AWS CLI, the upload fails with an access denied error. The engineer has s3:PutObject permission on the bucket. Which additional permission is most likely missing?
medium
A.kms:CreateKey
B.kms:Decrypt
C.s3:PutObjectAcl
✓ D.kms:GenerateDataKey
Why D: To upload an object with SSE-KMS, the IAM user or role must have kms:GenerateDataKey permission to generate a data key for encryption. Option A is correct because without it, the upload fails. Option B is wrong because kms:Decrypt is for decryption, not upload. Option C is wrong because kms:CreateKey is for creating keys, not using them. Option D is wrong because s3:PutObjectAcl is for ACLs, not encryption.
Variation 2. A company has an AWS Glue ETL job that reads data from an S3 bucket encrypted with SSE-S3. The job runs successfully, but the output written to another S3 bucket with SSE-KMS fails. The IAM role for the Glue job has s3:PutObject and kms:GenerateDataKey permissions. What is the most likely cause?
hard
✓ A.The IAM role is missing kms:Encrypt permission
B.The target S3 bucket policy denies s3:PutObject
C.The KMS key policy does not grant the Glue role kms:GenerateDataKey
D.The source bucket's encryption type is incompatible with the target
Why A: Option D is correct. Glue needs kms:Encrypt permission to write with SSE-KMS. Option A is wrong because SSE-S3 doesn't need KMS. Option B is wrong because S3 bucket policy is not the issue. Option C is wrong because KMS key policy needs to allow the role, but the role already has GenerateDataKey; missing Encrypt is more likely.
Variation 3. A company is using AWS Glue to process data stored in an S3 bucket that is encrypted with SSE-KMS. The Glue job fails with an 'Access Denied' error when trying to read the data. The IAM role used by the Glue job has permissions to read from the S3 bucket and to use the KMS key. What is the most likely cause of the failure?
hard
A.The S3 bucket is using SSE-S3 instead of SSE-KMS
B.The S3 bucket policy denies access to the Glue job
C.The KMS key is in a different AWS account
✓ D.The IAM role is missing the kms:Decrypt permission
Why D: Option D is correct because AWS Glue jobs need the kms:Decrypt permission on the KMS key to read data encrypted with SSE-KMS. The IAM role may have the S3 read permissions but lack the kms:Decrypt permission. Option A (SSE-S3) is not relevant as the bucket uses SSE-KMS. Option B (bucket policy) could also be a cause, but the most common issue is missing kms:Decrypt. Option C (cross-account access) is less likely if the key is in the same account.
Last reviewed: Jun 20, 2026
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