MLS-C01 Data Engineering Practice Question

Exhibit

Refer to the exhibit.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Resource": "arn:aws:s3:::data-lake-bucket/*",
      "Condition": {
        "StringEquals": {
          "s3:x-amz-server-side-encryption": "aws:kms"
        }
      }
    },
    {
      "Effect": "Deny",
      "Action": "s3:PutObject",
      "Resource": "arn:aws:s3:::data-lake-bucket/*",
      "Condition": {
        "StringNotEquals": {
          "s3:x-amz-server-side-encryption": "aws:kms"
        }
      }
    }
  ]
}

An IAM policy is attached to a data engineering role that writes to an S3 bucket. The policy is shown in the exhibit. What is the effect of this policy?

⚠ Common exam trap

The trap here is that candidates often overlook the `Deny` effect on `s3:GetObject` and assume the policy only restricts writes, missing that reading is also conditionally denied unless the object uses SSE-KMS.

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 role must use SSE-KMS when writing objects; reading is allowed only if the object is encrypted with SSE-KMS

The IAM policy uses a `Condition` block with `s3:x-amz-server-side-encryption` set to `aws:kms`, which enforces that any `PutObject` request must include SSE-KMS encryption. The `Deny` effect on `s3:GetObject` when encryption is not `aws:kms` ensures that reading objects without SSE-KMS is blocked. This combination allows writing only with SSE-KMS and reading only of objects encrypted with SSE-KMS, making option D correct.

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 role can write objects with any encryption, but reading is restricted to SSE-KMS only
Why it's wrong here
The Deny statement prevents writing without SSE-KMS.
✗
The role can read and write any object without encryption restrictions
Why it's wrong here
The policy restricts both read and write to SSE-KMS encrypted objects.
✗
The role can only read objects; writing is always denied
Why it's wrong here
The first statement allows PutObject with SSE-KMS, so writing is not always denied.
✓
The role must use SSE-KMS when writing objects; reading is allowed only if the object is encrypted with SSE-KMS
Why this is correct
The Allow statement grants GetObject only when SSE-KMS is specified, and the Deny statement enforces SSE-KMS for PutObject.

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

MLS-C01 Data Engineering Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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