Magento sites need optimization to load fast and provide a good user experience. Speeding up a site increases sales and improves SEO. Factors that impact load time include network transfers and the resource-intensive nature of Magento. Benchmarking tools like APDEX, Funkload, Yslow and Pagespeed help measure performance and set goals, such as loading the homepage in under 1.5 seconds. Architectures must be sized properly and include techniques like splitting front and back ends, enabling caching, and using a CDN. The Nitrogento extension automates optimizations like blocking caching, sprite generation, and asset minification to significantly improve performance.