Strange Story About Attempt to Improve Web Performance

Sometimes, as a test engineer, you have to argue with product owners about seemingly obvious things.

Andrey Enin
4 min readMar 24, 2023

It was at the time when I was testing a media web service with around 16 million average monthly visitors.

There was a legacy page with a list of snippets of some content (images and descriptions) and a [Show more] button at the bottom.

Mockup of a service’s page with performance issues — Strange story about attempt to improve web performance
Mockup of a service’s page with performance issues.

The problem with such a simple page was its performance — it took over 10 sec to load just a bunch of snippets. Why?

The investigation showed:

1. Lighthouse performance audit gave a score = 1!

2. Frontend requested only one backend handler for data, but

  • this handler responded with a 9 Mb body (JSON file), which took to load for nearly 1 sec. A client (user’s browser) had to parse this file to render it, which, of course, took a long time due to the large amounts of data;
  • JSON data contained too much unnecessary information. Frontend used only a fraction of the data for the snippet, but dozens of key-value pairs remained unused.

3. And it turned out to be much worse: if the user clicked on the [Show more] button, the page opened with about three thousands snippets (that is all snippets contained in a 9 Mb body without pagination).

  • And for all thousands of snippets, image thumbnails began to load simultaneously. User could get around 100 Mb with no reason.

That sounds terrifying, especially for users with poor and not unlimited internet and low-performance devices.

A development team quickly found a number of the easiest ways of improvements (less efforts / maximum profit):

  1. Load only necessary data from backend (even without pagination we could reduce size of the body for 50%);
  2. Add real pagination on frontend and API (load data by chunks and only when it required);
  3. Implement lazy loading for images.

We (the engineering team) asked product owners to give us time to fix those issues (we came up with the described tasks and time estimates), but got the answer «no».

Strangely, maybe we did not explain the severity of the problem well?

Then, we provided a list of examples of the relationship between page load speed and conversion:

  • Pinterest increased search engine traffic and sign-ups by 15% when they reduced perceived wait times by 40%;
  • COOK increased conversions by 7%, decreased bounce rates by 7%, and increased pages per session by 10% when they reduced average page load time by 850 milliseconds;
  • BBC found they lost an additional 10% of users for every additional second their site took to load;
  • DoubleClick by Google found 53% of mobile site visits were abandoned if a page took longer than 3 seconds to load;
  • AutoAnything reduced page load time by half and saw a boost of 12% to 13% in sales;
  • Mobify found that decreasing their homepage’s load time by 100 milliseconds resulted in a 1,11% uptick in session-based conversion;
  • Walmart discovered that improving page load time by one second increased conversions by 2%;
  • 1 second of load lag time would cost Amazon $1,6 billion in sales per year;
  • Amazon increased revenue by 1% for every 100 ms of improvement;
  • A lag time of 400 ms results in a decrease of 0,44 % traffic;
  • For every 100 ms of improvement, they grew incremental revenue by up to 1%;
  • 47% of consumers expect a web page to load in 2 seconds or less;
  • 40% of people abandon a website that takes more than 3 seconds to load;
  • Yahoo increased traffic by 9% for every 400 ms of improvement
  • Mozilla got 60 million more Firefox downloads per year, by making their pages 2,2 seconds faster;
  • Shopzilla says, that reducing page load time from 6 seconds to 1,2 seconds delivers a 12% increase in revenue and a 25% increase in pages viewed;
  • 79% of customers who run into any kind of performance issues on your website are less likely to buy from you again;
  • 0–4 second load time is best for conversion rates;
  • The first 5 seconds of page load time have the highest impact on conversion rates;
  • A site that loads in 1 second has a conversion rate 5x higher than a site that loads in 10 seconds.

Did it convince product owners that performance matters? — No!

The answer was like: «We understand your concern, but so far our user base is growing linearly, we are not going to invest resources into fixing technical debts».

Down with technical debt, while there is growth — What this graph does not say is that if there are no problems now, it does not mean that they will not appear in the future
What this graph does not say is that if there are no problems now, it does not mean that they will not appear in the future.

It was incredibly frustrating (why not taking care of a technical debt is bad is not the topic of this story). What engineers saw as a problem and thought that it affects the product and users, managers did not even consider it as an issue requiring attention.

I suppose that product owners were not conscious enough, but developers were — they fixed most of the performance issues in their spare time within a couple of months.

Further reading:

Font for mockup illustration: Norum Ipnum.



Andrey Enin

Quality assurance engineer: I’m testing web applications, APIs and do automation testing.