Never Take Your Eye Off the Ball: Four mistakes Shopzilla made so you don’t have to

At Velocity 2009, Shopzilla became the poster child for web performance optimization when they reported some pretty powerful numbers. The company radically re-architected its entire online operation with an eye toward reducing infrastructure and improving performance. In the end, they sped up their average page load time from 6 seconds to 1.2 seconds and experienced a 7-12% increase in conversion rate and a 25% increase in page views.

Shopzilla’s huge quantifiable success became a rallying point for many of us, so you can imagine how excited I was to hear that the company’s lead architect, Tim Morrow, would be speaking at Velocity 2010 to update us on Shopzilla’s latest numbers. And you can imagine how surprised — and impressed — I was when Tim’s session ended up being a clear, frank discussion of how Shopzilla dropped the ball.

In the months following its enormous performance success, Shopzilla saw its page load times slowly creep from an impressive sub-2 seconds up to more than 5 seconds. Users started to complain about the site’s slowness, sending feedback like “I will not come back to this site again” and the always-cogent “It sucks.”

I’ve embedded the YouTube video of Tim’s presentation below (it’s only 11 minutes long and worth watching), but here are the key mistakes he identified:

  1. No front-end measurement. It’s not enough to fine tune your site. You need to continually test and monitor your performance.
  2. Constant feature development. Shopzilla introduces several new features every week, which adds up. Says Tim: “There’s a tension between features and performance. The added complexity and constant change tends to unravel performance.”
  3. Poorly implemented third-party content. There’s no getting away from ads and widgets, but these need to be either designed in such a way that they don’t eat up valuable bandwidth or prioritized so that they’re not the first page elements to load.
  4. Waiting too long to tackle performance problems. It’s easier and cheaper to deal with problems early in the development cycle.

I often cite the Golden Gate Bridge as an analogy for manually tuning site performance. As soon as you finish painting it, it’s time to start all over again.

But it pays off. After rallying a performance task force and tweaking performance on just a few key pages, Shopzilla saw a 0.4% increase in their conversion rate, which translated into just a two-month ROI.

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