A retail company runs its e-commerce platform on Azure App Service. The platform is configured with an autoscale rule that adds web server instances when CPU usage exceeds 75%. During a holiday flash sale, traffic surges from a baseline of 1,000 concurrent users to over 100,000 concurrent users within minutes. The platform automatically provisions additional instances to handle the load, and once the sale ends, it scales back down. This ability to rapidly adjust resources to meet varying demand is a direct example of which fundamental characteristic of cloud computing?