A business wants its mission-critical application to handle increased user traffic by adding more instances of its web server. Which cloud concept describes adding more instances of a resource?

Horizontal scaling, also known as scaling out, involves adding more instances of a resource, such as virtual machines or containers, to distribute the workload. This allows the application to handle increased demand by running across multiple servers. Vertical scaling (scaling up) would involve increasing the resources (CPU, RAM) of an existing server, which eventually hits limits and doesn't distribute the load. Elasticity is the ability to automatically scale resources up or down based on demand, but the method of adding more instances is horizontal scaling. High availability ensures an application remains accessible even if some components fail, but it doesn't specifically describe the act of adding more instances to handle traffic.