The trick to make it super fast is to predict where the user might be viewing 1 second from now. If an animation is in progress, that's an easy prediction. If

The trick to make it super fast is to predict where the user might be viewing 1 second from now. If an animation is in progress, that's an easy prediction. If the user is using a mouse, they'll generally scroll or pan but not both. If the user is on a touch screen, again the gestures are limited. When you have your predictions, you start loading the those things.