A company wants EC2 instances to be added and removed automatically so capacity scales up and down with changing workloads. Which AWS feature or service provides this functionality?

Amazon EC2 Auto Scaling automatically adjusts the number of EC2 instances in your application based on demand. This ensures your application maintains performance and reduces costs by scaling out during peak loads and scaling in during idle periods. DynamoDB is a NoSQL database service, not for scaling EC2 instances. EC2 Spot Instances are a cost-effective option for fault-tolerant workloads but don't inherently provide automatic scaling based on demand. The AWS Snow Family is for physical data transfer, not for dynamic scaling of compute resources.