There is a fast and simple tweak for Magento that allows you to speed up the loading time and backend of your Magento website. With this tweak, products and categories are placed in a special table with good indexes, meaning that Magento doesn't have to go through the entire database, but is able to search the necessary products very efficiently.
To enable this option, you must login to your Magento backend. Subsequently, navigate to System > Configuration > Catalog > Frontend.
Once there, find the option Use Flat Catalog Category en Use Flat Catalog Product . Change both these options into yes. Magento will subsequently be busy making calculations for a while, since it is to populate the special table. Once this is completed, empty the caches of your site under the heading -> cache management.
From that moment on, your site will be using the flat catalog tables, which should lead to significantly faster load times.