Issue link: https://read.uberflip.com/i/1146286
The Performance Golden Rule | 5 Second, frontend improvements typically require less time and fewer resources. Reducing backend latency involves projects such as redesigning application architec- ture and code, finding and optimizing critical code paths, adding or modifying hard- ware, distributing databases, etc. These projects take weeks or months. Most of the frontend performance improvements described in the following chapters involve best practices, such as changing web server configuration files (Chapters 3 and 4); plac- ing scripts and stylesheets in certain places within the page (Chapters 5 and 6); and combining images, scripts, and stylesheets (Chapter 1). These projects take hours or days—much less than the time required for most backend improvements. Third, frontend performance tuning has been proven to work. Over 50 teams at Yahoo! have reduced their end user response times by following the best practices described here, many by 25% or more. In some cases, we've had to go beyond these rules and identify improvements more specific to the site being analyzed, but gener- ally, it's possible to achieve a 25% or greater reduction just by following these best practices. At the beginning of every new performance improvement project, I draw a picture like that shown in Figure A-1 and explain the Performance Golden Rule: Only 10–20% of the end user response time is spent downloading the HTML docu- ment. The other 80–90% is spent downloading all the components in the page. The rest of this book offers precise guidelines for reducing that 80–90% of end user response time. In demonstrating this, I'll cover a wide span of technologies: HTTP headers, JavaScript, CSS, Apache, and more. Because some of the basic aspects of HTTP are necessary to understand parts of the book, I highlight them in Chapter B. After that come the 14 rules for faster performance, each in its own chapter. The rules are listed in general order of priority. A rule's applicability to your specific web site may vary. For example, Rule 2 is more appropriate for commercial web sites and less feasible for personal web pages. If you follow all the rules that are applicable to your web site, you'll make your pages 25–50% faster and improve the user experi- ence. The last part of the book shows how to analyze the 10 top U.S. web sites from a performance perspective.