A web application is running on three EC2 instances behind an Application Load Balancer. Sporadic spikes in traffic are causing performance to suffer. Which design will automatically scale the application to handle variable load?

The correct solution is to deploy the application to an Auto Scaling group with a target tracking scaling policy and attach the ALB. Auto Scaling groups are designed to automatically adjust the number of EC2 instances based on demand, ensuring high availability and fault tolerance. A target tracking policy allows you to define a target metric (e.g., average CPU utilization or ALB request count per target) and AWS will automatically scale the group to maintain that target, effectively handling sporadic traffic spikes. Increasing instance size (first incorrect option) is vertical scaling and doesn't efficiently handle variable load; it's also a manual process if done via a CloudWatch alarm. An EventBridge rule (second incorrect option) can trigger actions, but an Auto Scaling group with a scaling policy is the dedicated and more robust solution for dynamic instance management. Scheduled scaling (fourth incorrect option) is for predictable load patterns, not sporadic spikes.