Velocity 09: Philip Dixon, "Shopzilla's Site Redo - You Get What You Measure"

Posted in Development on June 28, 2009

Founded in 1996, Shopzilla is a leading comparison shopping service. The company’s mission is to enable shoppers to quickly and easily find compare and buy anything, sold by virtually anyone, anywhere. Each month, Shopzilla connects millions of consumers with thousands of stores. On Cyber Monday 2008, Shopzilla was proud to be ranked by ComScore as the #1 Comparison Shopping Engine and #11 overall retail site (as measured by average daily unique visitors: 1.95M).

In the summer of 2007, Shopzilla decided to finally do something about the fact that our websites ( and had become so slow for our users. Our original consumer sites were built on a monolithic design and had over 6-7 years become difficult to change and more difficult still to scale engineering teams to support. We had a platform with more than 6 years of accrued technical debt, but were presented with a classic dilemma for an established internet market player: Can we really afford the costs – real and opportunity – and the risks of re-engineering a site platform responsible for all of our revenue? Perhaps even more importantly: What will we really get from a site overhaul? Will the site really be faster? Can we really innovate more easily given a “better” software design? Will we even complete the project, or will we be forced to abandon it mid-stream? Will we make more money?


Just in time for the 2008 holiday shopping crush, Shopzilla successfully completed a 16 month re-engineering initiative and released and on a new site platform we call “site 2”. At the time of release, the sites’ functionally were the same as “before”, but the consumer experience changed dramatically. The following are some highlights of the many benefits realized by our re-engineering:


  • Dramatically faster page load times for our users: The site 2 average full-page download time is now 1.2 seconds (sub-second above the fold) for – down from 6-9 seconds! (1.9 seconds for Bizrate due to banners).
  • Huge improvements in availability: The “platform” is much more than the software. As we re-engineered the site platform, a significant area of design focus was on sustainability, support and management of the entire delivery ecosystem – from the software, to the people, to the systems. The result has been a significant increase in both uptime and availability. In Q4, 2008, our site availability was 99.97%, up from 99.51% in Q3 – and an average of 99.65%. In terms of innovation, we have been able to maintain this availability rate into 2009 while increasing our platform release velocity by more than 200%. After all, it doesn’t matter much if your site is fast if people can’t get to it…
  • Significant decrease in total cost of ownership: The site hardware (server) stack for site 2 requires approx 10% of the physical resources of site 1. From a capacity perspective, even that 10% is overbuilt by 2.5x based on our capacity forecasts through 2009.
  • We make (a lot) more money! Based on a number of factors which we will explore in the talk, the site 2 stack has delivered a 5% – 12% lift in top-line revenue (depending on traffic source and Bizrate vs. Shopzilla)! This revenue lift comes primarily from intra-session (financial) performance drivers, but also in part due to an increase in sessions from the search engines. (details in the talk :)

Our talk will explore Shopzilla’s site 2 initiative in great detail. We will discuss:

  • The Shopzilla site (2) architecture – A detailed and highly technical review of the technology choices made by the Shopzilla team, the trade-offs and the architecture itself. We will also take a frank look at wrong turns, poor choices and lessons learned in the design and implementation process.
  • You get what you measure – Why any team should obsess over this concept – from technical SLA’s to financial performance metrics.
  • What actually made the difference – A discovery of what really matters. Remember that part of our initiative was focused on simply making the site easier to support and innovate. In retrospect, what where the key drivers of our performance gains (both technical and financial)?
  • How to sell an initiative like this. We will discuss how the technology leaders at Shopzilla sold this initiative in the face of so many questions – and how we kept the senior leadership and company at-large excited for more than 16 months.
  • The platform is bigger than the software – it includes the infrastructure, the people and the leadership.


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Tags: Scalability, Performance, Development, oreilly media, Velocity 2009, Shopzilla