- A
The CodeDeploy agent is not installed or running on the EC2 instances.
Without the agent, instances cannot run deployment scripts.
- B
The IAM instance profile does not have permissions to download from Amazon S3.
Why wrong: While necessary, missing permissions would produce a different error.
- C
The application revision is not a compressed archive.
Why wrong: CodeDeploy can deploy individual files if specified in appspec.
- D
The deployment configuration 'AllAtOnce' is incompatible with Auto Scaling groups.
Why wrong: AllAtOnce is valid for Auto Scaling groups.
Question 456 of 1,750
CodeDeploy AllAtOnce Deployment Failure: Missing Agent
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 company uses AWS CodeDeploy to deploy an 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 is set to 'AllAtOnce'. The application revision is a simple index.html. 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.
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 CodeDeploy agent is not installed or running on the EC2 instances.
The error message indicates that too many instances failed deployment, which is typical when the CodeDeploy agent is not running on the EC2 instances. With an 'AllAtOnce' deployment, all instances are targeted simultaneously, so if the agent is missing on every instance, all will fail immediately, causing the overall deployment to fail. The simple index.html revision is not the issue; the agent is required to execute the AppSpec file and pull the revision from S3 or GitHub.
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 CodeDeploy agent is not installed or running on the EC2 instances.
Why this is correct
Without the agent, instances cannot run deployment scripts.
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 IAM instance profile does not have permissions to download from Amazon S3.
Why it's wrong here
While necessary, missing permissions would produce a different error.
- ✗
The application revision is not a compressed archive.
Why it's wrong here
CodeDeploy can deploy individual files if specified in appspec.
- ✗
The deployment configuration 'AllAtOnce' is incompatible with Auto Scaling groups.
Why it's wrong here
AllAtOnce is valid for Auto Scaling groups.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the error is due to S3 permissions or archive format, but the generic 'too many instances failed' message points to a fundamental agent connectivity issue, not a permissions or file format problem.
Detailed technical explanation
How to think about this question
The CodeDeploy agent runs as a service on each EC2 instance and polls the CodeDeploy service for deployment instructions. If the agent is not installed or not running, the instance never reports back to the service, causing the deployment to time out and fail after the configured 'wait time' (default 1 hour for in-place deployments). In Auto Scaling groups, new instances launched by a scale-out event will automatically have the agent if the AMI or user data installs it; otherwise, deployments will consistently fail.
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.
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 |
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 CodeDeploy agent is not installed or running on the EC2 instances. — The error message indicates that too many instances failed deployment, which is typical when the CodeDeploy agent is not running on the EC2 instances. With an 'AllAtOnce' deployment, all instances are targeted simultaneously, so if the agent is missing on every instance, all will fail immediately, causing the overall deployment to fail. The simple index.html revision is not the issue; the agent is required to execute the AppSpec file and pull the revision from S3 or GitHub.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on DOP-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 of Amazon EC2 instances. 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 application is deployed to the instances using an in-place deployment. The instances are running Amazon Linux 2. What should the DevOps engineer check first?
medium- A.Check the security group rules for the EC2 instances.
- B.Check the application's port availability.
- ✓ C.Verify that the AWS CodeDeploy agent is installed and running on each EC2 instance.
- D.Verify that the IAM instance profile associated with the instances has the correct permissions.
Why C: The error message indicates that individual instances failed deployment, which is most commonly caused by the AWS CodeDeploy agent not running or not being installed on the EC2 instances. For an in-place deployment on Amazon Linux 2, the CodeDeploy agent must be installed and actively running to receive and execute deployment commands from the CodeDeploy service. If the agent is missing or stopped, the instance cannot participate in the deployment, leading to the 'too many individual instances failed' error.
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Last reviewed: Jul 4, 2026
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