Question

A company runs a stateless web application on EC2 instances behind an Application Load Balancer. All instances currently launch in a single Availability Zone within one Region. During a recent AZ outage, the entire application became unavailable for several hours. The team wants to improve fault tolerance so the application survives the loss of a single Availability Zone with no manual intervention, while keeping costs reasonable. Which change should the solutions architect make?

Accepted Answer

Configure the Auto Scaling group to span multiple subnets in different Availability Zones and register those subnets with the ALB.

Answer

Increase the instance size to a larger type and enable EC2 Auto Recovery on each instance.

Answer

Deploy a second copy of the application in another Region and use Route 53 failover routing.

Answer

Enable Multi-AZ for the Application Load Balancer and keep the Auto Scaling group in a single subnet.