DEA-C01 Data Security and Governance Practice Question
A data engineer is setting up a data pipeline that ingests streaming data from Amazon Kinesis Data Streams into an S3 data lake using Amazon Kinesis Data Firehose. The data contains personally identifiable information (PII). The security team requires that all data be encrypted at rest in S3 using an AWS KMS customer managed key (CMK) that is specific to the application. Additionally, the data must be encrypted in transit between all services. The engineer creates the KMS key and configures Firehose to use server-side encryption with the key for the S3 destination. However, Firehose delivery fails with an error indicating that the KMS key is not accessible. What is the most likely cause?
Answer choices
Why each option matters
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 does not grant the firehose.amazonaws.com service principal the required permissions.
Kinesis Data Firehose needs permission to use the KMS key. The key policy must grant the Firehose service principal (firehose.amazonaws.com) permission to call kms:GenerateDataKey and kms:Decrypt. Without this, Firehose cannot encrypt the data.
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 does not grant the firehose.amazonaws.com service principal the required permissions.
Why this is correct
Firehose must be allowed to use the key via the key policy.
- ✗
The Kinesis data stream is not encrypted at rest.
Why it's wrong here
The requirement is for S3 encryption; stream encryption is separate.
- ✗
The Firehose delivery stream is not in the same region as the KMS key.
Why it's wrong here
Cross-region KMS is allowed but may need additional permissions; however, the most likely cause is missing key policy.
- ✗
The S3 bucket policy does not grant the Firehose delivery stream access to write objects.
Why it's wrong here
The bucket policy would cause a different error, not a KMS access issue.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.