DVA-C02 Deployment Practice Question
A developer is using AWS CodeDeploy to deploy an application to an Auto Scaling group of EC2 instances. The developer wants to minimize the number of instances that are taken out of service at any given time during the deployment. Which predefined deployment configuration should the developer use?
⚠ Common exam trap
The trap here is that candidates might think 'HalfAtATime' is not a predefined configuration, but AWS CodeDeploy does offer 'HalfAtATime' as a predefined option. However, 'HalfAtATime' takes half the instances out of service at once, which does not minimize the number. The correct choice to minimize instances taken out of service is 'OneAtATime'.
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
✓
OneAtATime
The OneAtATime deployment configuration shifts traffic to one new instance at a time, ensuring that only a single instance is taken out of service during the deployment. This minimizes the number of instances removed from the Auto Scaling group at any given moment, which directly meets the developer's requirement to reduce service disruption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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AllAtOnce
Why it's wrong here
The AllAtOnce deployment configuration updates all instances within the Auto Scaling group simultaneously. This approach results in the entire application fleet being taken out of service for the duration of the deployment, leading to a complete service interruption. Consequently, it fails to minimize impact or maintain application availability during the update process, making it unsuitable for high-availability requirements.
- ✓
OneAtATime
Why this is correct
The OneAtATime deployment configuration updates instances sequentially, taking only one instance out of service at any given moment while the remaining instances continue to serve traffic. This rolling update strategy ensures that the application maintains high availability throughout the deployment process, significantly minimizing the impact on end-users. It is the most effective method for ensuring continuous service and reducing downtime in an Auto Scaling environment.
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HalfAtATime
Why it's wrong here
The HalfAtATime deployment configuration updates half of the instances in the Auto Scaling group concurrently. While better than AllAtOnce, this strategy still results in a substantial 50% reduction in available capacity during the deployment, which can significantly impact application performance and user experience. This level of disruption is considerably higher than updating one instance at a time, failing to achieve minimal impact.
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Custom with 50% at a time
Why it's wrong here
A custom deployment configuration set to update 50% of instances at a time, while offering flexibility, effectively mirrors the behavior and impact of the HalfAtATime strategy. This configuration would similarly take half of the application's capacity offline simultaneously, leading to a significant reduction in service availability. Therefore, despite being user-defined, it does not minimize impact as effectively as a OneAtATime approach.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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