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Difficulty: MediumAuto Scaling and Elasticity

An administrator manages an Amazon EC2 Auto Scaling group (ASG) configured with a target tracking scaling policy based on Average CPU Utilization. The application hosted on the instances requires 300300 seconds to fully bootstrap, configure services, and begin processing requests. During a sudden spike in traffic, the ASG launches a new instance. However, before that instance is fully initialized, the ASG launches another instance because the aggregate CPU utilization remains elevated. Which configuration adjustment will prevent the ASG from launching unnecessary instances while the newly launched instances are bootstrapping?

  1. Increase the estimated instance warmup time in the target tracking scaling policy to 300300 seconds.Answer
  2. B
    Increase the default cooldown period of the Auto Scaling group to 300300 seconds.
  3. C
    Enable detailed monitoring in the launch template used by the Auto Scaling group to transition metrics to 11-minute intervals.
  4. D
    Create an Amazon EventBridge rule that triggers an AWS Systems Manager Automation runbook to temporarily suspend the AlarmNotification scaling process during scale-out.

Answer

Increase the estimated instance warmup time in the target tracking scaling policy to 300300 seconds.
Increasing the estimated instance warmup time to 300300 seconds is the correct solution. For target tracking scaling policies, the estimated instance warmup parameter defines how long it takes for a newly launched instance to warm up. While an instance is warming up, its metrics are not included in the aggregate metric calculation for the group, and the Auto Scaling group will not trigger another scale-out action due to the elevated metrics.

Step-by-Step Solution

1
Analyze the scaling behavior under the current target tracking policy.
The target tracking policy does not wait long enough for the instance to bootstrap, leading to additional scale-out actions while the first instance is warming up.
By default, target tracking uses an estimated instance warmup. If the warmup is shorter than the actual bootstrap time, the ASG assumes the instance is warmed up but its CPU utilization is not yet contributing to the average, causing the ASG to scale out again.
2
Differentiate between the default cooldown period and estimated instance warmup.
The default cooldown period is confirmed to apply to simple scaling, whereas the target tracking scaling policy relies on estimated instance warmup.
This prevents misconfiguring the Auto Scaling group's default cooldown parameter, which has no effect on target tracking scaling behavior.
3
Adjust the estimated instance warmup time to match the application's bootstrap duration.
Setting the estimated instance warmup time to 300300 seconds ensures the Auto Scaling group will not launch subsequent instances until the warming instance completes bootstrapping.
This direct configuration parameter natively handles the bootstrap latency of new instances in target tracking scaling policies.

Key Concept

Configuring estimated instance warmup for target tracking scaling policies to handle application initialization latency.
Estimated Time:1m 30s
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Topics

Auto Scaling and Elasticity

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