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Question 983 of 1,740

SDLC Automation →easyMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the IAM role attached to the EC2 instance lacks the `kms:Decrypt` permission for the AWS KMS key used to encrypt the S3 object. This is because the CodeDeploy agent runs the `BeforeInstall` lifecycle hook script on the instance, and when that script attempts to download a package from an SSE-KMS encrypted S3 bucket, the AWS SDK or CLI on the instance must call KMS to decrypt the object. Without the `kms:Decrypt` action allowed in the instance’s IAM role policy for that specific key, the download fails, which causes the lifecycle hook to error out and triggers the overall deployment failure due to too many unhealthy instances. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how IAM permissions interact with encrypted resources in a deployment pipeline—a common trap is assuming the CodeDeploy service role handles decryption, when in fact the EC2 instance’s role must have the permission. Memory tip: “If the script can’t fetch, check the KMS decrypt on the EC2 role’s patch.”

DOP-C02 SDLC Automation Practice Question

This DOP-C02 practice question tests your understanding of sdlc automation. 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.

A DevOps engineer is setting up an AWS CodePipeline to deploy a web application to an EC2 instance using AWS CodeDeploy. The deployment group uses an in-place deployment configuration. The pipeline's deploy stage fails with the error: 'The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available, or some instances in your deployment group are experiencing problems.' The engineer checks the CodeDeploy logs on the instance and finds that the 'BeforeInstall' lifecycle hook script is failing. The script attempts to download a package from an Amazon S3 bucket that is encrypted with SSE-KMS. What is the MOST likely cause of the failure?

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 1easymultiple choice

Full question →

A
The EC2 instance does not have internet access to reach the S3 bucket.
Why wrong: If the instance is in a VPC without internet access, it might not be able to access S3 via public endpoint, but the error mentions a script failure, not a network error.
B
The S3 bucket name is misspelled in the 'BeforeInstall' script.
Why wrong: A misspelled bucket name would cause a different error (e.g., NoSuchBucket), not a KMS-related failure.
C
The IAM role attached to the EC2 instance lacks the 'kms:Decrypt' permission for the AWS KMS key used to encrypt the S3 object.
Without kms:Decrypt permission, the script cannot download the encrypted object, causing the hook to fail.
D
The CodeDeploy agent does not have permissions to read from the S3 bucket.
Why wrong: The CodeDeploy agent uses the instance's IAM role; if it lacks s3:GetObject, it would fail, but the error specifically points to the script failing, not the agent.

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 attached to the EC2 instance lacks the 'kms:Decrypt' permission for the AWS KMS key used to encrypt the S3 object.

The error occurs because the EC2 instance's IAM role lacks the `kms:Decrypt` permission for the AWS KMS key used to encrypt the S3 object. When the `BeforeInstall` script attempts to download the package, the AWS SDK or CLI on the instance must decrypt the object using the KMS key. Without this permission, the download fails, causing the lifecycle hook to fail and the overall deployment to abort due to too many failed instances.

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 EC2 instance does not have internet access to reach the S3 bucket.
Why it's wrong here
If the instance is in a VPC without internet access, it might not be able to access S3 via public endpoint, but the error mentions a script failure, not a network error.
✗
The S3 bucket name is misspelled in the 'BeforeInstall' script.
Why it's wrong here
A misspelled bucket name would cause a different error (e.g., NoSuchBucket), not a KMS-related failure.
✓
The IAM role attached to the EC2 instance lacks the 'kms:Decrypt' permission for the AWS KMS key used to encrypt the S3 object.
Why this is correct
Without kms:Decrypt permission, the script cannot download the encrypted object, causing the hook to fail.
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.
✗
The CodeDeploy agent does not have permissions to read from the S3 bucket.
Why it's wrong here
The CodeDeploy agent uses the instance's IAM role; if it lacks s3:GetObject, it would fail, but the error specifically points to the script failing, not the agent.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume the CodeDeploy agent handles all S3 access, but the script runs under the instance's IAM role, and missing KMS permissions are a common oversight when using encrypted artifacts.

Detailed technical explanation

How to think about this question

When an S3 object is encrypted with SSE-KMS, any request to download it must include the `x-amz-server-side-encryption-aws-kms-key-id` header and the caller must have `kms:Decrypt` permission for that specific KMS key. The AWS CLI or SDK automatically handles this, but the IAM role must grant the permission. In practice, the error message 'too few healthy instances' often masks the root cause, as CodeDeploy aggregates instance failures without exposing the exact script error in the pipeline output.

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.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The IAM role attached to the EC2 instance lacks the 'kms:Decrypt' permission for the AWS KMS key used to encrypt the S3 object. — The error occurs because the EC2 instance's IAM role lacks the `kms:Decrypt` permission for the AWS KMS key used to encrypt the S3 object. When the `BeforeInstall` script attempts to download the package, the AWS SDK or CLI on the instance must decrypt the object using the KMS key. Without this permission, the download fails, causing the lifecycle hook to fail and the overall deployment to abort due to too many failed instances.

What should I do if I get this DOP-C02 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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