AWS Certified Solutions Architect – Associate (SAA-C03) — Question 809

A company hosts an application on Amazon EC2 instances that run in a single Availability Zone. The application is accessible by using the transport layer of the Open Systems Interconnection (OSI) model. The company needs the application architecture to have high availability.

Which combination of steps will meet these requirements MOST cost-effectively? (Choose two.)

Answer options

• A. Configure new EC2 instances in a different Availability Zone. Use Amazon Route 53 to route traffic to all instances.
• B. Configure a Network Load Balancer in front of the EC2 instances.
• C. Configure a Network Load Balancer for TCP traffic to the instances. Configure an Application Load Balancer for HTTP and HTTPS traffic to the instances.
• D. Create an Auto Scaling group for the EC2 instances. Configure the Auto Scaling group to use multiple Availability Zones. Configure the Auto Scaling group to run application health checks on the instances.
• E. Create an Amazon CloudWatch alarm. Configure the alarm to restart EC2 instances that transition to a stopped state.

Correct answer: B, D

Explanation

Since the application is accessed via the transport layer (Layer 4), a Network Load Balancer is the ideal and cost-effective service for distributing traffic. To guarantee high availability across multiple zones, an Auto Scaling group spanning multiple Availability Zones must be used along with application health checks to automatically replace failed instances. Other options, such as using both an ALB and NLB or relying solely on Route 53, are either unnecessarily expensive or fail to provide automatic multi-AZ recovery.