Auto Trader is the UK's biggest car sales website. Search is the key piece of functionality and prior to the redevelopment it was very difficult to use and slow. The search works by choosing criteria that would reduce the options for the next criteria. For instance, when choosing the car Make it would filter the Model field. However each filter change would cause a refresh of the entire page.
We built a brand a new search system that worked in real time without refreshing the page every time the criteria were altered.