- A
The health check grace period on the Auto Scaling group is too short.
Correct. A short grace period causes instances to be considered unhealthy before the deployment finishes, triggering Auto Scaling to replace them and causing repeated failures.
- B
The target group deregistration delay is too long.
Why wrong: Incorrect. Deregistration delay affects how long in-flight requests are served, but it does not cause instances to fail the deployment health check.
- C
The CodeDeploy agent is not installed on the instances.
Why wrong: Incorrect. If the agent were missing, the first instance would fail immediately, not 'too many individual instances' over time.
- D
The deployment group is configured to skip the ELB health check.
Why wrong: Incorrect. Skipping the ELB health check would prevent health check failures from impacting the deployment, so this would not cause the error.
Quick Answer
The answer is that the health check grace period on the Auto Scaling group is too short. This is the most likely cause because when CodeDeploy uses the CodeDeployDefault.OneAtATime configuration, it takes each instance out of service from the Application Load Balancer, deploys the new application version, and then returns it to service. If the health check grace period expires before the instance can pass its health checks, the Auto Scaling group marks the instance as unhealthy and terminates it, triggering the "too many individual instances failed" error. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how CodeDeploy interacts with Auto Scaling health checks during rolling deployments. A common trap is to blame the deployment configuration or the application code, but the root cause is timing—the grace period must be long enough to accommodate the deployment and health check cycle. Memory tip: think "grace period = deployment buffer"—if it’s too short, healthy instances get terminated prematurely.
SOA-C02 Deployment, Provisioning, and Automation Practice Question
This SOA-C02 practice question tests your understanding of deployment, provisioning, and 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 team uses AWS CodeDeploy with a deployment configuration of CodeDeployDefault.OneAtATime to deploy a web application to an Auto Scaling group. Instances are behind an Application Load Balancer. The deployment fails with 'The overall deployment failed because too many individual instances failed deployment.' 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 health check grace period on the Auto Scaling group is too short.
The deployment fails because the health check grace period on the Auto Scaling group is too short. When CodeDeploy deploys one instance at a time (CodeDeployDefault.OneAtATime), the instance is taken out of service, updated, and then returned to the load balancer. If the grace period expires before the instance passes its health checks, the Auto Scaling group marks it as unhealthy and terminates it, causing the deployment to fail with 'too many individual instances failed.'
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 health check grace period on the Auto Scaling group is too short.
Why this is correct
Correct. A short grace period causes instances to be considered unhealthy before the deployment finishes, triggering Auto Scaling to replace them and causing repeated failures.
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 target group deregistration delay is too long.
Why it's wrong here
Incorrect. Deregistration delay affects how long in-flight requests are served, but it does not cause instances to fail the deployment health check.
- ✗
The CodeDeploy agent is not installed on the instances.
Why it's wrong here
Incorrect. If the agent were missing, the first instance would fail immediately, not 'too many individual instances' over time.
- ✗
The deployment group is configured to skip the ELB health check.
Why it's wrong here
Incorrect. Skipping the ELB health check would prevent health check failures from impacting the deployment, so this would not cause the error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the health check grace period with the deregistration delay or assume the issue is with the CodeDeploy agent, but the specific error 'too many individual instances failed' points to Auto Scaling terminating instances due to health check failures, not a deployment script or agent problem.
Detailed technical explanation
How to think about this question
The health check grace period (default 300 seconds in Auto Scaling) allows an instance to boot and stabilize before health checks begin. If this period is too short, the instance is considered unhealthy immediately after deployment, triggering a scale-in event. CodeDeploy's OneAtATime strategy expects each instance to complete its lifecycle (deregister, update, re-register, pass health checks) before proceeding to the next; a premature termination disrupts this flow and causes the overall deployment to 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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Deployment, Provisioning, and Automation — This question tests Deployment, Provisioning, and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The health check grace period on the Auto Scaling group is too short. — The deployment fails because the health check grace period on the Auto Scaling group is too short. When CodeDeploy deploys one instance at a time (CodeDeployDefault.OneAtATime), the instance is taken out of service, updated, and then returned to the load balancer. If the grace period expires before the instance passes its health checks, the Auto Scaling group marks it as unhealthy and terminates it, causing the deployment to fail with 'too many individual instances failed.'
What should I do if I get this SOA-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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Last reviewed: Jun 11, 2026
This SOA-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 SOA-C02 exam.
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