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Difficulty: MediumAuto Scaling and Elasticity

An e-commerce company operates an application on AWS where the frontend instances are managed by an Auto Scaling group (ASG). During scheduled flash sales, the company notices that CPU utilization spikes instantly on the active instances, causing the application to become temporarily unresponsive. However, the ASG fails to launch any new instances until exactly 55 minutes after the flash sale starts, despite a target tracking policy being active. The ASG's launch template does not have detailed monitoring enabled.

Which configuration adjustment will resolve the delay in the initial scale-out actions?

  1. A
    Adjust the step scaling policy to reduce the scale-out cooldown timer to 00 seconds, allowing immediate scaling when the metric threshold is breached.
  2. B
    Create a custom EventBridge rule that triggers the Auto Scaling policy directly when the scaling metric threshold is exceeded, bypassing the default metric collection latency.
  3. Enable detailed monitoring in the launch template of the Auto Scaling group so that metrics are sent to Amazon CloudWatch at 11-minute intervals.Answer
  4. D
    Attach an IAM policy with `iam:PassRole` permissions to the IAM instance profile of the EC2 instances, allowing the Auto Scaling service to execute scaling API calls.

Answer

Enable detailed monitoring in the launch template of the Auto Scaling group so that metrics are sent to Amazon CloudWatch at 11-minute intervals.
Enabling detailed monitoring in the launch template sends EC2 metrics such as CPU utilization to CloudWatch at 11-minute intervals instead of the default 55 minutes. This reduces the latency of alarm evaluation, permitting target tracking policies to scale out the group much more rapidly during traffic spikes.

Step-by-Step Solution

1
Analyze the observed delay pattern.
The delay is exactly 55 minutes, which matches the metric delivery interval of standard monitoring.
By default, basic or standard monitoring for EC2 instances posts metrics to CloudWatch at 55-minute intervals, delaying any scaling alarms built on these metrics.
2
Determine the scaling metric source configuration.
Standard monitoring is currently active because detailed monitoring is disabled in the launch template.
Auto Scaling groups inherit monitoring settings from their launch configurations or templates.
3
Select the appropriate resolution to reduce metric latency.
Enabling detailed monitoring on the launch template reduces the metric update interval to 11 minute.
This allows CloudWatch to receive metrics more frequently and evaluate the target tracking policy's threshold alarm within 11 minute of a load spike.

Key Concept

Standard vs. Detailed CloudWatch Monitoring for Auto Scaling Groups
Estimated Time:1m 30s
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Topics

Auto Scaling and Elasticity

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