DOP-C02 SDLC Automation Practice Question
An organization 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 engineer reviews the deployment logs and finds that the AppSpec file is correctly formatted and the scripts run successfully on some instances. What is the MOST likely cause?
⚠ Common exam trap
A common mix-up: candidates confuse deployment script success with overall deployment health, not realizing that CodeDeploy relies on the target group's health checks (configured via the Auto Scaling group's health check grace period) to determine if an instance is healthy after deployment.
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 for the Auto Scaling group is too short.
The error indicates that instances are failing the deployment health check after the AppSpec scripts run successfully. When the health check grace period for the Auto Scaling group is too short, instances may be marked unhealthy before the application has fully started and passed the target group health checks, causing CodeDeploy to consider them failed. This is the most likely cause because the scripts succeed on some instances but the overall deployment fails due to insufficient healthy instances.
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 on some instances.
Why it's wrong here
The CodeDeploy agent is not installed on some instances. If the agent is missing on certain instances, those instances cannot pull the deployment revision or execute the AppSpec file, so they would fail the deployment consistently on those instances. However, this is an instance-specific problem rather than a systemic timing issue: instances with the agent would deploy successfully, which does not match the described failure pattern where instances are terminated before the application starts. Additionally, if the agent were missing on all instances, every deployment would fail uniformly, not just intermittently or after a specific time window.
- ✗
The target group is not configured to route traffic to the instances.
Why it's wrong here
The target group is not configured to route traffic to the instances. This would prevent the load balancer from sending traffic to the instances, but CodeDeploy itself does not depend on the target group's routing rules to perform the deployment. If the target group were misconfigured, the ALB would report unhealthy targets and connection failover might occur, but the instances themselves would still complete the deployment lifecycle unless the load balancer health check is tied to the deployment group's health check configuration. In the described scenario, the failure is specifically due to instances being prematurely terminated by Auto Scaling, not due to lack of inbound traffic routing, so this option does not explain the deployment failure.
- ✓
The health check grace period for the Auto Scaling group is too short.
Why this is correct
The health check grace period for the Auto Scaling group is too short. When an Auto Scaling group launches a new instance, it waits for the health check grace period before evaluating the instance's EC2 health status. If this period expires before CodeDeploy has installed and started the application, the ASG may consider the instance unhealthy and terminate it, interrupting the deployment. This causes the deployment to fail on those instances, even though the CodeDeploy agent and IAM permissions are fine. The correct fix is to increase the ASG health check grace period to cover the full deployment duration, including bootstrapping and application startup.
- ✗
The IAM role assigned to the EC2 instances does not have sufficient permissions.
Why it's wrong here
The IAM role assigned to the EC2 instances does not have sufficient permissions. If the instance profile lacks the required CodeDeploy permissions (e.g., codedeploy:GetDeployment, codedeploy:GetDeploymentSpec, or S3 read access), the agent cannot poll for or fetch the deployment revision, causing every instance with that role to fail in the same way. This is a uniform, reproducible failure that occurs for all deployments on all instances, not a timing-dependent issue where only some instances are terminated. Therefore, while insufficient IAM permissions could certainly break deployments, the symptom here is instance termination by Auto Scaling, which points to the health check grace period rather than a permissions misconfiguration.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.