Which feature of AWS allows for the automated scaling of resources based on demand?

AWS Auto Scaling is a feature designed specifically for automatically adjusting the amount of resources based on current demand. This capability enhances both performance and cost efficiency by ensuring that the number of instances or resources allocated to an application can increase or decrease in response to the resource utilization metrics set by the user. For example, during traffic spikes, AWS Auto Scaling can automatically launch new instances to handle the increased load, and during periods of lower activity, it can terminate instances to reduce costs.

In contrast, AWS Config focuses on the monitoring and management of AWS resource configurations, allowing users to assess compliance and track changes over time. AWS Elastic Beanstalk provides an environment for deploying and scaling web applications but relies on auto-scaling settings configured within AWS Auto Scaling for resource scaling. Meanwhile, AWS CloudFormation is a service that helps users define and provision AWS infrastructure using code, but it does not provide automated scaling functionality on its own.

Thus, AWS Auto Scaling stands out as the correct choice, as its primary function is to manage resource scaling in alignment with fluctuating demand.