A SysOps administrator monitors and maintains the availability of resources in an AWS environment.

Comprehensive and Detailed Explanation From Exact Extract of AWS CloudOps Documents:

The requirement is to fix performance degradation from predictable peak CPU load without service disruptions. The most reliable and operationally standard approach is horizontal scaling with an Auto Scaling group driven by CloudWatch metrics/alarms (or target tracking). Launching additional instances and distributing traffic (typically behind a load balancer) increases capacity while keeping existing instances serving requests—no reboot or stop/start required.

Option D meets the requirement because Auto Scaling can add capacity when CPU exceeds a threshold and remove capacity when demand falls. This improves performance during peak periods and maintains availability. It is also operationally efficient: scaling actions are automated, consistent, and can be tuned with cooldowns/health checks.

Options A and C describe vertical scaling (instance resize). Resizing an EC2 instance type generally requires stopping the instance, changing the type, and starting it again—this is disruptive for a single-instance web server and often causes downtime. Option B (restarting the application) directly introduces disruption and does not address underlying capacity constraints; it can also worsen customer impact during peaks.