DEA-C01 Data Ingestion and Transformation Practice Question

Exhibit

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Resource": "arn:aws:s3:::data-lake-bucket/*"
    },
    {
      "Effect": "Allow",
      "Action": [
        "kinesis:DescribeStream",
        "kinesis:GetShardIterator",
        "kinesis:GetRecords"
      ],
      "Resource": "arn:aws:kinesis:us-east-1:123456789012:stream/clickstream"
    }
  ]
}

Refer to the exhibit. An IAM policy for an AWS Lambda function. The Lambda function is triggered by an S3 event (object created) and needs to read from a Kinesis stream. However, the function fails with access denied when trying to read from Kinesis. What is the most likely cause?

⚠ Common exam trap

The DEA-C01 exam often tests the interaction between Kinesis SSE-KMS and Lambda IAM permissions, trapping candidates who assume that Kinesis read permissions alone are sufficient without considering the KMS key policy.

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 Kinesis stream is encrypted with a customer managed KMS key, and the Lambda function lacks kms:Decrypt permission

When a Kinesis stream is encrypted with a customer managed KMS key, the Lambda function must have the `kms:Decrypt` permission on that key to read data from the stream. Without this permission, the Lambda function will receive an access denied error even if it has the necessary Kinesis actions (e.g., `kinesis:GetRecords`) allowed in its IAM policy. The S3 event trigger only invokes the function; it does not grant Kinesis access.

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 Lambda function is not in the same region as the Kinesis stream
Why it's wrong here
Cross-region access isn't the blocker: Lambda reads Kinesis streams in its own region, and the stem's access-denied error points to the execution role's IAM policy, not geography. It is tempting because co-locating resources reduces latency and data-transfer costs, so region alignment is a genuine design consideration — just not the cause of an authorisation failure.
✗
The Lambda function does not have permission to list S3 buckets
Why it's wrong here
Listing S3 buckets is irrelevant: the S3 event trigger already delivers the object, and the failure occurs reading Kinesis. This permission would matter only if the function itself enumerated buckets, for example to discover which bucket to process.
✓
The Kinesis stream is encrypted with a customer managed KMS key, and the Lambda function lacks kms:Decrypt permission
Why this is correct
Reading from a Kinesis stream encrypted with a customer managed KMS key requires kms:Decrypt in the Lambda execution role. The S3 event trigger and stream read permissions may be correct, but the missing KMS grant causes the access denied error.
✗
The S3 bucket policy denies access to the Lambda function
Why it's wrong here
The S3 bucket policy governs access to S3 objects, not Kinesis. Since the trigger fires and the error arises on the Kinesis read, an S3 denial cannot produce it. Bucket policies would be the cause if the function failed reading the triggering object.

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

Go deeper

DEA-C01 Data Ingestion and Transformation Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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