Ajax Performance

What is a page? Part 2

When I finished my presentation at the Ajax Experience Boston, one of the attendees asked if we (Gomez) run into problems educating our customers about approaches to understanding Ajax performance. It’s a good question; in the performance testing industry, years of experience with the page-by-page traditional model of developing and testing applications has lulled many into the mistaken assumption that certain metrics can be applied as benchmarks to all applications.

One such outmoded tool (the sliderule of the web development world, if you will) is the assumption that any page taking more than N seconds to load will lead to customer frustration and abandonment. Currently, N is defined as 7 and is determined by the mathematical function

N = 10 - (years since 2000 % 2)

The problem with this assumption, as touched on by Brad Neuberg in the article I mentioned in my previous post, is that any definition of load time that doesn’t include user perception is inherently flawed. A 12 second time to load all content isn’t an issue if the user sees an application ready for interaction in 5 seconds, with the rest of the Ajaxy bells and whistles being loaded behind the scenes. Isn’t that the whole point of the Ajax model, hiding as much network latency from the end user as possible?

Occasionally we’ll encounter a customer who wants to know the magic event fired by the browser at the point that the Ajax application is loaded, in the hopes of applying the 7 second benchmark. But there’s typically at least one developer or manager within the group who understands that the world doesn’t work that way anymore. Often, we’re helping that developer explain to management or the operations group why the higher total load time of the Ajax application is less important than the blisteringly fast user perceived load time the developer worked so hard to create.

The only way to define the performance of an Ajax application is to consider everything from the end user’s perspective. In the next (and perhaps last) post in the ‘What is a page?’ series, I will provide an Ajax-appropriate definition of page load time and explain how to use this metric to design, build, and release new applications.