Steve Souders, the famous Web performance expert, has a great article about building fast web applications.
Formspider has built-in solutions for every point he raises in the article.
AJAX: AJAX is built into the Formspider Framework. Everything is AJAX by default. You don’t even worry about it. It just works.
Caching: The users download the Formspider JS library once when they access the application the very first time and then it is cached until there is a newer version of the library. Every screen a user accesses while she is using the application is cached for the life time of her session.