← DVA-C02·Amazon Web Services

Question 904 of 1,616

Deployment →mediumMultiple ChoiceObjective-mapped

CodeDeploy OneAtATime Fails When Single Instance Drop Below Minimum Healthy

This DVA-C02 practice question tests your understanding of deployment. 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 company uses AWS CodeDeploy to deploy a web application to an Auto Scaling group. The deployment fails with the error 'The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available for deployment, or some instances in your deployment group are experiencing problems.' The deployment group has a minimum of 2 instances and a maximum of 4. The deployment configuration is CodeDeployDefault.OneAtATime. 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.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

A
The deployment group's maximum instances is set to 4, which exceeds the number of instances in the Auto Scaling group.
Why wrong: Incorrect because the maximum is not exceeded; it is a limit, not a current count.
B
The Auto Scaling group has only 2 instances, and one instance fails during deployment, leaving less than the required healthy instances.
Correct because the deployment configuration requires one instance at a time, and with only 2 instances, a failure reduces healthy count below threshold.
C
The IAM role attached to the instances does not have sufficient permissions to download the revision from Amazon S3.
Why wrong: Incorrect because the error message does not indicate permission issues.
D
The revision is not properly zipped or the AppSpec file is missing.
Why wrong: Incorrect because the error message points to instance health, not revision format.

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 Auto Scaling group has only 2 instances, and one instance fails during deployment, leaving less than the required healthy instances.

The deployment configuration CodeDeployDefault.OneAtATime deploys to one instance at a time, and the deployment group has a minimum of 2 healthy instances. If one instance fails during deployment, only 1 healthy instance remains, which is below the minimum required threshold of 2. This causes CodeDeploy to stop the deployment and mark it as failed, as it cannot maintain the required number of healthy 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 deployment group's maximum instances is set to 4, which exceeds the number of instances in the Auto Scaling group.
Why it's wrong here
Incorrect because the maximum is not exceeded; it is a limit, not a current count.
✓
The Auto Scaling group has only 2 instances, and one instance fails during deployment, leaving less than the required healthy instances.
Why this is correct
Correct because the deployment configuration requires one instance at a time, and with only 2 instances, a failure reduces healthy count below threshold.
Clue confirmation
The clue words "most likely", "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The IAM role attached to the instances does not have sufficient permissions to download the revision from Amazon S3.
Why it's wrong here
Incorrect because the error message does not indicate permission issues.
✗
The revision is not properly zipped or the AppSpec file is missing.
Why it's wrong here
Incorrect because the error message points to instance health, not revision format.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may overlook the interaction between the deployment configuration (OneAtATime) and the minimum healthy instances setting, assuming any instance failure is due to a code or permission issue rather than a capacity constraint.

Detailed technical explanation

How to think about this question

CodeDeploy's deployment configuration defines the rate at which instances are updated and the minimum number of healthy instances required during deployment. With CodeDeployDefault.OneAtATime, the deployment proceeds one instance at a time, and the system checks that the number of healthy instances never drops below the deployment group's minimum healthy instances setting (default is 100% of the fleet size, but here it's implicitly 2). If an instance fails, the healthy count drops below the threshold, triggering a rollback or failure. This behavior is critical in production environments where maintaining availability is paramount.

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 DVA-C02 question test?

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

What is the correct answer to this question?

The correct answer is: The Auto Scaling group has only 2 instances, and one instance fails during deployment, leaving less than the required healthy instances. — The deployment configuration CodeDeployDefault.OneAtATime deploys to one instance at a time, and the deployment group has a minimum of 2 healthy instances. If one instance fails during deployment, only 1 healthy instance remains, which is below the minimum required threshold of 2. This causes CodeDeploy to stop the deployment and mark it as failed, as it cannot maintain the required number of healthy instances.

What should I do if I get this DVA-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", "minimum / minimize". 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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Same concept, more angles

1 more ways this is tested on DVA-C02

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A company uses AWS CodeDeploy to deploy a web application to an Auto Scaling group. The deployment fails with the error 'The overall deployment failed because too many individual instances failed deployment'. The deployment configuration is set to CodeDeployDefault.OneAtATime. What is the most likely cause of this failure?

medium

A.The instances in the Auto Scaling group are not running a supported operating system.
B.The deployment configuration should be changed to AllAtOnce to avoid this error.
C.The IAM role for CodeDeploy does not have sufficient permissions.
✓ D.The deployment failed on a single instance, causing the overall deployment to fail because the minimum number of healthy hosts was not maintained.

Why D: CodeDeployDefault.OneAtATime deploys to one instance at a time. The deployment stops immediately if a single instance fails, because the deployment configuration expects no failures. The error 'too many individual instances failed' is triggered by that single failure, since the deployment cannot proceed to the next instance without violating the minimum healthy hosts requirement, which is set to maintain availability.

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This DVA-C02 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 DVA-C02 exam.