Case Study

Messages Image(3126392774).jpeg, part of the Cox Automotive Group, is a car search website that aims to make the process of finding and selling the right car as easy as possible for buyers and sellers. In 2014 NCC Group was commissioned to load test the website ahead of a TV advertising campaign.

Overview were planning a major TV advertising campaign and needed to know how their site would cope with the projected traffic. They knew they were going to load test the site, but this in itself raised a lot of questions. For example, just how much traffic could be expected? They were entering uncharted territory, so this was not easy to answer. They also had to decide what user journeys would be most representative and how many would be required to test the different parts of the system.

The Context were planning a major TV advertising campaign and needed to know that the website would cope under the pressure of the extra traffic.

Our Solution knew that a consistent, reliable load testing platform was critical, and NCC Group, with its access to Tier 1 connectivity and stable test environment, was the ideal candidate.

It targeted three key user journeys, starting from the home page, the SEO campaign landing page and the news page. While had a very capable web team, they weren’t experienced in load testing, and they therefore opted for a managed service from NCC Group.

During the planning phase, worked closely with NCC Group to agree parameters such as ramp-up time (the time it takes to build up to the total number of simulated users), think time (how long each simulated user remains on a page) and the number of simulated users per test. also supplied NCC Group with datasets to allow the load testing agent to search for different makes of car and enter different postcodes.

NCC Group then tested the site in such a way that the number of users active at any one time and the overall length of the scenario were predefined. This method is typically used where, as here, the key factor is reaching and maintaining a certain number of concurrent users.

As well as load testing the selected pages, NCC Group also used its Performance Analyser tool to crawl the entire site. This provided:

  • Information on the biggest, slowest and worst performing pages
  • Details of render times and other key metrics
  • A filmstrip view of pages loading, as real users would see them
  • Recommendations for improving performance.


Overall, the results were positive for They showed that the work they had put into preparing the site for the anticipated peaks in traffic had, for the most part, paid off.

However, the testing process did pick up a number of errors and opportunities for further optimisation. What’s more, the Performance Analyser crawl meant that NCC Group experts were able to look at the entire site in detail and suggest improvements.

Fortunately, had planned well. They had scheduled in the testing phase early enough to act on the results. This meant they could make a number of front-end changes to help their site perform well during the campaign.

Aaron Fenwick, project and operations manager,, said:

“We were acutely aware that a successful ad campaign depended on having a website that would stand up to the traffic it generated. It was therefore essential to factor in load testing and to make sure that we had time to act on the results.

“We got two things out of the process with NCC Group. The first was peace of mind. While load testing can never give you a 100% guarantee, we had full confidence in NCC Group’s testing regime, and we were as sure as we could be that the site would cope. Fortunately, we were right.

“The second thing we got was insight into what was slowing down various pages on our site. This enabled us to carry out important remedial work ahead of the campaign. As a result, we were able to make sure that the site delivered optimum performance at the most important time.

“All this has delivered real financial benefits. The fact that the site not only coped during the campaign, but also performed well means that we’ve been able to make the most of the traffic that came our way. So we’re confident that we’ve maximised revenue.

“But it’s also about cost. Some of the front-end optimisation techniques proposed by NCC Group’s consultant helped us to reduce our bandwidth usage and therefore cut our expenditure. And all this is before we even consider the impact on our brand. Convenience is key for our customers, so a fast, reliable website is essential.

“We’re delighted that NCC Group helped us to achieve this.”

The engagement was also a positive one from NCC Group’s point of view:

“I really enjoyed working with They had planned very well and knew just what they could expect to get out of the testing process. They were also refreshingly open to suggestions when it came to front-end optimisation, and I’m pleased to have played a small part in their campaign’s success” Abi Pollock, technical consultant, NCC Group Web Performance.

Published date:  25 June 2015

Mia Davis