The correct answer is the IAM policy statement granting `kms:Decrypt` and `kms:GenerateDataKey` actions on the KMS key resource. This is because AWS Glue jobs interacting with SSE-KMS encrypted S3 data require two distinct KMS permissions: `kms:Decrypt` to read existing encrypted objects, and `kms:GenerateDataKey` to create a new data key for writing encrypted data back to S3. Without `kms:GenerateDataKey`, the Glue job cannot encrypt new objects during write operations, even if it has decrypt permissions. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding that SSE-KMS is a server-side encryption method where S3 calls KMS on your behalf, so the IAM role must explicitly allow both actions. A common trap is choosing only `kms:Decrypt` or `kms:Encrypt`—remember that writing encrypted data requires generating a data key, not just encrypting. Memory tip: “Decrypt to read, GenerateDataKey to seed” the write operation.
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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 configuring AWS Glue jobs to access data stored in Amazon S3. The data is encrypted using server-side encryption with AWS KMS (SSE-KMS). The Glue job needs to read and write data to the S3 bucket. Which IAM policy statement should be added to the Glue job's IAM role to allow it to use the KMS key?
To read and write data encrypted with SSE-KMS, AWS Glue needs both `kms:Decrypt` (to read existing encrypted data) and `kms:GenerateDataKey` (to create a new data key for writing encrypted data). `kms:GenerateDataKey` is required because S3 uses a data key to encrypt objects, and the caller must generate that key via KMS. Option B correctly includes both actions, allowing the Glue job to perform read and write operations on the SSE-KMS encrypted bucket.
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.
Missing kms:GenerateDataKey for writing; also kms:Encrypt alone is not sufficient for SSE-KMS writes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume `kms:Encrypt` is needed for writing encrypted data, but S3 SSE-KMS actually requires `kms:GenerateDataKey` because the encryption is done with a derived data key, not by calling `kms:Encrypt` directly.
Detailed technical explanation
How to think about this question
When S3 uses SSE-KMS, the actual object encryption is performed using a unique data key, not the KMS key directly. The `kms:GenerateDataKey` action returns a plaintext data key for encryption and a ciphertext version for storage; the plaintext key is discarded after use, and the ciphertext key is stored with the object. Without `kms:GenerateDataKey`, the Glue job cannot initiate the write operation because S3 cannot obtain a data key to encrypt the new object.
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 Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: {"Effect":"Allow","Action":["kms:Decrypt","kms:GenerateDataKey"],"Resource":"*"} — To read and write data encrypted with SSE-KMS, AWS Glue needs both `kms:Decrypt` (to read existing encrypted data) and `kms:GenerateDataKey` (to create a new data key for writing encrypted data). `kms:GenerateDataKey` is required because S3 uses a data key to encrypt objects, and the caller must generate that key via KMS. Option B correctly includes both actions, allowing the Glue job to perform read and write operations on the SSE-KMS encrypted bucket.
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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