AWS Certified Solutions Architect – Associate (SAA-C03) — Question 272

A company runs an internal browser-based application. The application runs on Amazon EC2 instances behind an Application Load Balancer. The instances run in an Amazon EC2 Auto Scaling group across multiple Availability Zones. The Auto Scaling group scales up to 20 instances during work hours, but scales down to 2 instances overnight. Staff are complaining that the application is very slow when the day begins, although it runs well by mid-morning.

How should the scaling be changed to address the staff complaints and keep costs to a minimum?

Answer options

• A. Implement a scheduled action that sets the desired capacity to 20 shortly before the office opens.
• B. Implement a step scaling action triggered at a lower CPU threshold, and decrease the cooldown period.
• C. Implement a target tracking action triggered at a lower CPU threshold, and decrease the cooldown period.
• D. Implement a scheduled action that sets the minimum and maximum capacity to 20 shortly before the office opens.

Correct answer: C

Explanation

Target tracking scaling with a lower CPU threshold and a decreased cooldown period allows the Auto Scaling group to respond aggressively to early morning traffic spikes, scaling out quickly to prevent performance degradation. Scheduled actions that immediately scale the group to 20 instances (Options A and D) are less cost-effective because they run maximum capacity regardless of actual demand. Step scaling (Option B) requires manual threshold configuration and is generally less responsive and harder to optimize than target tracking for maintaining a specific metric target.