Developing nopCommerce we always pay attention to high performance rate for future sites on our platform. By today nopCommerce powers large stores that work extremely good, and our own store demo gets 100/100 at Google PageSpeed.
To gain the same result for your store you need to make sure that all the settings were made in a proper way. In this performance guide, we will show you how: https://www.nopcommerce.com/nopcommerce-performance-guide