← MLS-C01·Amazon Web Services

Question 1,706 of 1,755

Data Engineering →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the IAM role 'firehose-role' does not exist in the AWS account. This error occurs because the CloudFormation template specifies a static ARN for the role, including a hardcoded account ID, and when the stack is deployed in a different account or the role is missing, the Firehose delivery stream is unable to assume the role during creation. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of IAM trust policies and cross-account permissions, often appearing as a trap where candidates overlook the static account ID in the ARN. A common memory tip is to always verify that IAM roles referenced in templates exist in the target account, as Firehose requires explicit trust to write to destinations like S3 or Redshift. Remember: if the role ARN doesn’t match the account, the assumption fails.

MLS-C01 Data Engineering Practice Question

This MLS-C01 practice question tests your understanding of data engineering. 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.

Exhibit

Refer to the exhibit.

CloudFormation snippet:
"MyKinesisStream": {
  "Type": "AWS::Kinesis::Stream",
  "Properties": {
    "Name": "data-stream",
    "ShardCount": 2,
    "RetentionPeriodHours": 168,
    "StreamEncryption": {
      "EncryptionType": "KMS",
      "KeyId": "alias/aws/kinesis"
    }
  }
}

"MyFirehose": {
  "Type": "AWS::KinesisFirehose::DeliveryStream",
  "Properties": {
    "DeliveryStreamType": "KinesisStreamAsSource",
    "KinesisStreamSourceConfiguration": {
      "KinesisStreamARN": { "Fn::GetAtt": ["MyKinesisStream", "Arn"] },
      "RoleARN": "arn:aws:iam::123456789012:role/firehose-role"
    },
    "S3DestinationConfiguration": {
      "BucketARN": "arn:aws:s3:::my-bucket",
      "RoleARN": "arn:aws:iam::123456789012:role/firehose-role"
    }
  }
}

Refer to the exhibit. A team deploys this CloudFormation stack. The Kinesis stream is created, but the Firehose delivery stream fails to create with a 'Resource handler returned message: Unable to assume role' error. What is the most likely cause?

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.

Question 1hardmultiple choice

Full question →

Exhibit

Refer to the exhibit.

CloudFormation snippet:
"MyKinesisStream": {
  "Type": "AWS::Kinesis::Stream",
  "Properties": {
    "Name": "data-stream",
    "ShardCount": 2,
    "RetentionPeriodHours": 168,
    "StreamEncryption": {
      "EncryptionType": "KMS",
      "KeyId": "alias/aws/kinesis"
    }
  }
}

"MyFirehose": {
  "Type": "AWS::KinesisFirehose::DeliveryStream",
  "Properties": {
    "DeliveryStreamType": "KinesisStreamAsSource",
    "KinesisStreamSourceConfiguration": {
      "KinesisStreamARN": { "Fn::GetAtt": ["MyKinesisStream", "Arn"] },
      "RoleARN": "arn:aws:iam::123456789012:role/firehose-role"
    },
    "S3DestinationConfiguration": {
      "BucketARN": "arn:aws:s3:::my-bucket",
      "RoleARN": "arn:aws:iam::123456789012:role/firehose-role"
    }
  }
}

A
The shard count of 2 is too low for Firehose to read from.
Why wrong: Incorrect: Firehose can read from streams with any shard count.
B
The Kinesis stream is encrypted with KMS, but Firehose does not have permission to decrypt.
Why wrong: Incorrect: The error is about assuming the role, not decryption.
C
The retention period of 168 hours is too long for Firehose.
Why wrong: Incorrect: Firehose does not care about retention period.
D
The IAM role 'firehose-role' does not exist in the AWS account.
Correct: The role ARN is hardcoded; if the role is missing, Firehose cannot assume it.

Full breakdown with real-world context →

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 IAM role 'firehose-role' does not exist in the AWS account.

The Firehose role 'firehose-role' is specified with a static ARN that includes an account ID. If the stack is deployed in a different account, or if the role does not exist, the assumption fails. Option A (role does not exist in the account) is the most likely. Option B (stream encryption) is not related. Option C (retention period) is fine. Option D (shard count) is fine.

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.

✗
The shard count of 2 is too low for Firehose to read from.
Why it's wrong here
Incorrect: Firehose can read from streams with any shard count.
✗
The Kinesis stream is encrypted with KMS, but Firehose does not have permission to decrypt.
Why it's wrong here
Incorrect: The error is about assuming the role, not decryption.
✗
The retention period of 168 hours is too long for Firehose.
Why it's wrong here
Incorrect: Firehose does not care about retention period.
✓
The IAM role 'firehose-role' does not exist in the AWS account.
Why this is correct
Correct: The role ARN is hardcoded; if the role is missing, Firehose cannot assume it.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

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.
Use explanations to understand the rule behind the answer.

TExam Day Tips

Underline the problem statement mentally.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.

What to study next

Got this wrong? Here's your next step.

Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

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FAQ

Questions learners often ask

What does this MLS-C01 question test?

Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The IAM role 'firehose-role' does not exist in the AWS account. — The Firehose role 'firehose-role' is specified with a static ARN that includes an account ID. If the stack is deployed in a different account, or if the role does not exist, the assumption fails. Option A (role does not exist in the account) is the most likely. Option B (stream encryption) is not related. Option C (retention period) is fine. Option D (shard count) is fine.

What should I do if I get this MLS-C01 question wrong?

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?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 20, 2026

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