DVA-C02 Deployment Practice Question
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?
⚠ Common exam trap
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.
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.
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
A "maximum instances" setting in a CodeDeploy deployment group, or related configuration like MinimumHealthyHosts, defines an upper bound or a threshold, not a current state or a strict requirement for the *number* of instances to exist. If the Auto Scaling group has 2 instances and the maximum is 4, it simply means the deployment *could* handle up to 4 instances, but it doesn't fail because there are *fewer* than 4. The error would likely be related to *minimum* healthy hosts during deployment, not a maximum capacity mismatch, making this option incorrect.
- ✓
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
This scenario directly addresses a common CodeDeploy failure mode when using conservative deployment strategies like CodeDeployDefault.OneAtATime on small Auto Scaling groups. If the Auto Scaling group has only two instances, and one instance fails its health checks or application startup during the deployment, the number of healthy instances immediately drops to one. If the deployment configuration's MinimumHealthyHosts threshold requires more than one healthy instance (e.g., 50% of 2 instances, which rounds up to 1, but if the next step requires taking another instance out of service, it would fail), or if the deployment is configured to halt if any instance fails, the deployment will stop due to insufficient healthy hosts, preventing further degradation.
- ✗
The IAM role attached to the instances does not have sufficient permissions to download the revision from Amazon S3.
Why it's wrong here
Permission errors, specifically those related to downloading revisions from Amazon S3, typically manifest as explicit "Access Denied" messages within the CodeDeploy agent logs (/var/log/aws/codedeploy-agent/codedeploy-agent.log) or directly in the CodeDeploy console events. An error message indicating a failure due to insufficient healthy instances strongly suggests that the CodeDeploy agent successfully downloaded the revision and initiated the deployment steps. The problem then occurred during the application installation, configuration, or post-install health checks on the instance itself, leading to its unhealthiness, rather than an initial access issue.
- ✗
The revision is not properly zipped or the AppSpec file is missing.
Why it's wrong here
Issues with the revision package format, such as an improperly zipped file, corrupted archive, or a missing AppSpec.yml file, would typically trigger a distinct set of error messages from CodeDeploy. These errors would explicitly state problems like "No AppSpec file found," "Invalid revision format," or "Deployment failed due to AppSpec validation error." An error message focused on instance health or a failure to meet minimum healthy host requirements implies that the revision was successfully downloaded and processed, but the subsequent application deployment or health checks on the target instances failed, causing them to become unhealthy.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.