Alibaba Cloud Certified Associate (ACA) 2025 – 400 Free Practice Questions to Pass the Exam

An alarm trigger task not executing successfully in Alibaba Cloud Auto Scaling can indeed occur if the group has reached its maximum capacity. When the scaling policy is designed to add new instances based on specific conditions, reaching the maximum capacity of the scaling group inhibits any further scaling actions. This means that even if an alarm is triggered due to high resource utilization or other specified metrics, the system cannot scale out by adding more instances because the configured upper limit has been hit.

In regards to the other options, having all instances running the CloudMonitor agent is necessary for monitoring but does not directly affect the successful execution of alarm trigger tasks. Availability of instance types ensures that new instances can be provisioned, but it doesn't guarantee execution if the capacity limit is already reached. Similarly, a properly configured scaling policy is essential for executing scaling actions, but if the group is at maximum capacity, even a well-configured policy cannot trigger a successful action. Thus, the condition of reaching maximum capacity directly leads to the failure of the alarm trigger task to execute as intended.