AWS DevOps Engineer Professional Practice Test

What might cause an inconsistency in application versions after a CodeDeploy rolling update?

1. All instances must be updated before deployment

2. CodeDeploy does not support rolling updates

3. An auto-scaling event during deployment

4. A network issue with the CodeDeploy service

The correct answer is: An auto-scaling event during deployment

In the context of a CodeDeploy rolling update, an auto-scaling event can lead to inconsistencies in application versions because it can dynamically modify the number of instances in a deployment group while the update is in progress. If instances are added or removed due to auto-scaling, the application versions across different instances might not be synchronized. For example, if new instances come online with the latest application version while some existing instances are still being updated, this creates a situation where multiple versions of the application are running simultaneously within the same deployment group. By contrast, the other options suggest conditions that do not align with the mechanics of CodeDeploy. The requirement for all instances to be updated before deployment is not accurate, as rolling updates are designed to update instances gradually rather than all at once. Additionally, while CodeDeploy does support rolling updates, network issues might disrupt communication but are less likely to cause version inconsistencies than the dynamic nature of auto-scaling events. This understanding affirms that auto-scaling events are a critical factor in potential version discrepancies during deployment.