Exam AZ-104 Topic 16 Question 253 Discussion

Explanation:
As cooling period and scale in and scale out durations are not displayed in the graphical view, so we need to consider the default values as below for these settings.
Cool down (minutes) : The amount of time to wait before the rule is applied again so that the autoscale actions have time to take effect. Default is 5 minutes.
Duration : The amount of time monitored before the metric and threshold values are compared. Default is 10 minutes.
Box 1: 4 virtual machines
The Autoscale scale out rule increases the number of VMs by 2 if the CPU threshold is 80% or higher for more than or equals to 10 mins due to default duration for scale in and out is 10 minutes. Since CPU utilization at 85% only lasts for 6 mins , it does not trigger the rules.
Hence no of virtual machines will be same as the initial value which is 4.
Box 2: 4 virtual machines
The Autoscale scale in rule decreases the number of VMs by 4 if the CPU threshold is 30% or lower for more than or equal to 10 mins. due to default duration for scale in and out is 10 minutes . Since CPU utilization at 30% only lasts for 6 mins , it does not trigger the rules. Hence after first 6 mins instance count will be same as initial count as 4. After that CPU utilization reached to 50% for 6 mins , which again would not trigger the scale in rule. Therefore no of virtual machines will be same as the initial value which is 4.
References:
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/autoscale-overview
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/autoscale-best-practices
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/autoscale-common-scale-patterns