DOP-C02 SDLC Automation Practice Question
A team 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.' The instances are healthy and can connect to the CodeDeploy service. What is the most likely cause?
⚠ Common exam trap
It's easy for candidates to assume the error is due to network or permissions issues (like S3 access or IAM roles) because those are common causes, but the question explicitly states instances are healthy and can connect to CodeDeploy, shifting the root cause to the application-level scripts or configuration.
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 appspec.yml file or lifecycle event scripts have errors.
The error 'too many individual instances failed deployment' indicates that the deployment failed on the instances themselves, not at the infrastructure level. Since the instances are healthy and can connect to CodeDeploy, the most likely cause is that the appspec.yml file or the lifecycle event scripts (e.g., hooks like BeforeInstall, AfterInstall) contain errors that cause the deployment to fail on each instance. This is a common issue when scripts have syntax errors, missing dependencies, or incorrect paths.
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 Auto Scaling group launch configuration is incorrect.
Why it's wrong here
Although a faulty launch configuration can prevent instances from joining the Auto Scaling group or cause them to be terminated immediately, the question states the instances are healthy and running. Launch configuration issues would manifest as provisioning failures, health check failures, or inability to register with the load balancer, not as lifecycle event script execution errors. Since the deployment proceeds to run scripts and fails at that stage, the launch configuration is not the root cause.
- ✗
The deployment group is not configured with the correct service role.
Why it's wrong here
An incorrect or missing service role prevents CodeDeploy from orchestrating the deployment at the API level, resulting in immediate failures such as 'AccessDenied' when attempting to register the deployment or access Amazon S3. It does not influence the content or execution of lifecycle event hooks on the instance. Because scripts are actually running and producing errors, the service role is clearly sufficient for the deployment to proceed.
- ✓
The appspec.yml file or lifecycle event scripts have errors.
Why this is correct
The appspec.yml file controls the order and content of lifecycle events such as ApplicationStop, BeforeInstall, and AfterInstall. If the file is malformed, references a nonexistent script, or a referenced hook script exits with a non-zero status, CodeDeploy treats that instance as failed and reports 'ScriptFailed' or 'InvalidLifecycleEventName'. Because the deployment reaches the script execution stage and then errors, the appspec definition and its scripts are the most direct cause.
- ✗
The target revision is not accessible from the instances.
Why it's wrong here
If the target revision (the application bundle in S3 or GitHub) were inaccessible, the CodeDeploy agent would fail early during the DownloadBundle phase with an error such as 'Unable to download revision' or 'AccessDenied'. The agent never would invoke lifecycle event scripts, because the scripts are contained within the downloaded bundle. Since the deployment progresses to execute lifecycle hooks, the revision was successfully retrieved and this option cannot explain the observed failure.
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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.