Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 130 discussion

The correct answer is B. To maintain the desired performance across all instances in the Amazon EC2 Auto Scaling group, the solutions architect should use a target tracking policy to dynamically scale the Auto Scaling group. A target tracking policy allows the Auto Scaling group to automatically adjust the number of EC2 instances in the group based on a target value for a metric. In this case, the target value for the CPU utilization metric could be set to 40% to maintain the desired performance of the application. The Auto Scaling group would then automatically scale the number of instances up or down as needed to maintain the target value for the metric. https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-scaling-simple-step.html

target tracking policy = maintain

B is the correct answer, since target scaling monitors cloudwatch metrics, while simple/step scaling monitors cloudwatch alarms.

40% CPU for best performance is a "target tracking" policy for scaling so B is correct. A: Wrong policy CD: Won't achieve 40% CPU

https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-scaling-simple-step.html

I really don't get what kind of software running like a car with the most economical fuel speed range, but well, the answer is B

The application performs best when the CPU utilization of the EC2 instances is at or near 40%. Target tracking will maintain CPU utilization at 40%. When CloudWatch detects that the average CPU utilization is beyond 40%, it will trigger the target tracking policy to scale out the auto scaling group to meet this target utilization. Once everything is settled and the average CPU utilization has gone below 40%, another scale in action will kick in and reduce the number of auto scaling instances in the auto scaling group.

The key reasons are: A target tracking policy allows defining a specific target metric value to maintain, in this case 40% CPU utilization. Auto Scaling will automatically add or remove instances to keep utilization at the target level, without manual intervention. This will dynamically scale the group to maintain performance as load changes. A simple scaling policy only responds to breaching thresholds, not maintaining a target. Scheduled actions and Lambda would require manual calculation and updates to track utilization. Target tracking policies are the native Auto Scaling feature designed to maintain a metric at a target value.

Target tracking policy is the most appropriate choice. This policy allows ASG to automatically adjust the desired capacity based on a target metric, such as CPU utilization. By setting the target metric to 40%, ASG will scale the number of instances up or down as needed to maintain the desired CPU utilization level. This ensures that the application's performance remains optimal. A suggests using a simple scaling policy, which allows for scaling based on a fixed metric or threshold. However, it may not be as effective as a target tracking policy in dynamically adjusting the capacity to maintain a specific CPU utilization level. C suggests using an Lambda to update the desired capacity. While this can be done programmatically, it would require custom scripting and may not provide the same level of automation and responsiveness as a target tracking policy. D suggests using scheduled scaling actions to scale up and down ASG at predefined times. This approach is not suitable for maintaining the desired performance in real-time based on actual CPU utilization.

B of course.

B seem to the correct response. With a target tracking scaling policy, you can increase or decrease the current capacity of the group based on a target value for a specific metric. This policy will help resolve the over-provisioning of your resources. The scaling policy adds or removes capacity as required to keep the metric at, or close to, the specified target value. In addition to keeping the metric close to the target value, a target tracking scaling policy also adjusts to changes in the metric due to a changing load pattern.

target tracking - CPU at 40%

Option B

B is correct

Option B. Target tracking policy. https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-scaling-target-tracking.html

B CPU utilization = target tracking

B is the answer