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Difficulty: MediumAuto Scaling and Elasticity

A fleet of Amazon EC2 instances is managed by an Auto Scaling group that uses target tracking based on average CPU utilization. The application hosted on these instances takes approximately 6 minutes to complete its boot sequence and begin serving traffic. During scale-out events, the Auto Scaling group launches multiple waves of redundant instances before the first new instance can actively handle requests, resulting in temporary over-provisioning. Which configuration change will address this issue?

  1. A
    Increase the default cooldown period of the Auto Scaling group to 360 seconds.
  2. B
    Enable detailed monitoring in the Auto Scaling group launch template to send EC2 metrics at 1-minute intervals.
  3. Increase the estimated instance warmup time in the target tracking policy to at least 360 seconds.Answer
  4. D
    Create an Amazon EventBridge rule that triggers an AWS Systems Manager Automation document to suspend the Launch process during scaling events.

Answer

Increase the estimated instance warmup time in the target tracking policy to at least 360 seconds.
Increasing the estimated instance warmup time in the target tracking policy to at least 360 seconds ensures that the Auto Scaling group does not launch additional instances while the recently launched instances are bootstrapping. During the warmup period, instances are not counted toward the average metrics of the Auto Scaling group, preventing the policy from triggering further scale-out events prematurely.

Step-by-Step Solution

1
Analyze the scaling behavior and policy type.
The Auto Scaling group uses a target tracking scaling policy, and the application initialization delay is approximately 6 minutes (360 seconds).
Target tracking scaling policies evaluate metrics continuously but need to know how long a newly launched instance takes to warm up before contributing to the group's aggregate metrics.
2
Identify the parameter that controls metric aggregation timing for new instances.
The target tracking policy uses the estimated instance warmup parameter, which pauses further scale-out evaluations for the newly launched instance during its initialization.
Adjusting the default cooldown has no effect on target tracking policies, and changing monitoring frequency does not stop premature scaling.
3
Configure the estimated instance warmup parameter to cover the bootstrap period.
Setting the estimated instance warmup to 360 seconds or more prevents the target tracking policy from launching redundant instances during the 6-minute boot phase.
This stabilizes the scaling process and avoids over-provisioning.

Key Concept

Auto Scaling target tracking and estimated instance warmup configuration
Estimated Time:1m 30s
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Topics

Auto Scaling and Elasticity

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