AWS Certified Solutions Architect – Associate (SAA-C02) — Question 307

A company is launching an ecommerce website on AWS. This website is built with a three-tier architecture that includes a MySQL database in a Multi-AZ deployment of Amazon Aurora MySQL. The website application must be highly available and will initially be launched in an AWS Region with three Availability
Zones. The application produces a metric that describes the load the application experiences.
Which solution meets these requirements?

Answer options

• A. Configure an Application Load Balancer (ALB) with Amazon EC2 Auto Scaling behind the ALB with scheduled scaling.
• B. Configure an Application Load Balancer (ALB) and Amazon EC2 Auto Scaling behind the ALB with a simple scaling policy.
• C. Configure a Network Load Balancer (NLB) and launch a Spot Fleet with Amazon EC2 Auto Scaling behind the NLB.
• D. Configure an Application Load Balancer (ALB) and Amazon EC2 Auto Scaling behind the ALB with a target tracking scaling policy.

Correct answer: D

Explanation

An Application Load Balancer (ALB) is the ideal choice for routing HTTP/HTTPS traffic for a three-tier web application, and a target tracking scaling policy allows the Auto Scaling group to dynamically scale in and out based on the application's custom load metric. Scheduled scaling (Option A) is unsuitable because load changes are dynamic rather than time-bound, and simple scaling (Option B) is less efficient and responsive than target tracking. Using a Network Load Balancer with Spot Fleet (Option C) is inappropriate for a standard high-availability web layer that requires Layer 7 routing and reliable On-Demand instances.