The author, Cal Henderson, is an expert in PHP, MySQL, and Perl. He currently serves as the architect at Flickr and is also a special advisor for Vitamin. In this article, he focuses on how to make the user experience as fast as possible, including the download of the initial page, subsequent page downloads, and resource downloads that occur as the application progresses and content changes. This article is suitable for network engineers to read. Special thanks to htmlor for the excellent translation.