How to Prepare Your Website for Holiday Shopping Rush with Load Testing

By Yuri Kovalov, PFLB

The biggest sales season of the year is fast approaching, bringing peak loads to online stores and mobile apps. E-commerce platform owners can achieve record profits during this period, but only if they ensure the reliability and speed of their websites in advance. Modern shoppers aren't willing to wait.

According to Akamai, 49% of users expect a website to load in 2 seconds, while 30% expect it to load in just 1 second. If these expectations aren't met, half the users leave, and 22% never return. This is why preparing a website for peak loads, including thorough system testing and identifying and eliminating potential bottlenecks, is a priority for businesses and insurance against potential losses.

The better the testing, the higher the chances of retaining customers. Below are best practices for preparing systems for the peak sales season.

1. Analyze Past Performance

The first step is to analyze past years' performance. Review how your system handled peak loads, identify critical bottlenecks, and examine the geographic regions from which users accessed your platform. By pinpointing these areas, load generators can be strategically positioned to replicate traffic patterns more accurately, reflecting real user demand across different locations. This analysis will help avoid repeating past mistakes and lay the groundwork for detailed load planning.

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It's also helpful to estimate the potential costs if the site crashes or if a significant percentage of visitors leave due to delays. By doing so, you can better appreciate the importance of testing and allocate the necessary investment.

2. Set Up the Testing Environment

To ensure safe and effective testing, create a test clone of your platform that fully mirrors the live environment. Performance testing on the actual website can lead to unexpected failures and a poor customer experience. Only conduct tests on the production site as a last resort, carefully considering the associated risks.

The test environment should include all elements of the live configuration: server settings, databases, and hardware capabilities. With modern cloud technologies, cloning the environment is much easier and allows for a reliable assessment of system performance under near-realistic loads.

3. Define Realistic Load Conditions

To make testing as effective as possible, you need to define realistic load conditions that reflect real user actions on the site. Statistics from previous seasons or analytics tools (e.g., Google Analytics) can help model typical user behaviors: navigating from the homepage to product catalogs, using the search function, and completing purchases. If any additional functionality (e.g., new pages related to the sale) is introduced for the peak period and is expected to be heavily used, be sure to include it in the load profile.

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A well-defined load profile can segment users based on actions aligned with the statistical data — for instance, 20% navigate from the homepage to the product catalog, 5% log in to their accounts, 10% use the search function, and so on. This type of load profile allows for a realistic emulation of audience behavior, regardless of the total number of users, and provides an accurate assessment of how the system handles real-world load scenarios.

4. Implement Tests to Create the Load

The next step is to create virtual users to mimic actual customer behavior. Load testing platforms, such as JMeter, allow you to define various scenarios and distribute users across pages according to the load profile. We recommend that experienced engineers set up this process, as successfully creating realistic scenarios requires specific programming and testing skills.

5. Conduct Load Testing at Different Levels

Testing should include checks at standard, peak, and stress load levels. Can the website handle 10,000 or 100,000 users in 1 hour quickly and without errors? Stress tests reveal the platform's limits and allow you to see how it handles sudden traffic spikes. A system may perform well under a typical load, but how will it respond if the user flow suddenly doubles or even triples? And what will happen if the load unexpectedly increases many times over? It's crucial to answer these questions — not only to understand when performance issues might arise, but also to develop an action plan to minimize losses in such situations.

We recommend running long-duration tests (12-48 hours) to identify potential memory leaks and slowdowns that may occur with extended usage.

6. Conduct Client-Side Testing

Many performance issues can arise on the client side. For instance, if your site loads slowly in the Microsoft Edge browser or at low connection speeds, this can put users off. Test client-side performance as thoroughly as server-side performance. Slow page loading may not only be due to server load, but also to how the page behaves in the user's browser. For example, poorly optimized JavaScript can significantly slow page rendering. Your application should be adapted to work across various browsers and device types. During testing, it's helpful to consider different connection speeds, such as Wi-Fi, 3G, and 4G, to understand how the application performs under varying network conditions.

Since users in different regions may experience different loading speeds, it's also important to take geolocation into account. Users expect the application to work quickly and stably, regardless of the situation. If you have an in-house development team, involve them in analyzing application performance during load tests — this will help identify and address bottlenecks in the system more efficiently.

7. Monitor Performance in Real Time

Even after you successfully complete all the tests, real-time monitoring is crucial during sales periods. Use monitoring tools to track key metrics and respond quickly to potential issues. Monitor response times, CPU load, memory, disk utilization, database metrics, metrics on balancers, etc. Analyzing these metrics will allow you to promptly identify deviations from the norm and prevent possible failures.

Which Testing Tool?

There are numerous automated testing tools, such as LoadRunner, Apache JMeter, and PFLB. It's essential to select the tool that meets your business requirements. Preparing for Black Friday and other sales events requires a comprehensive approach and thorough testing. Success during the high season depends not only on your platform's performance but also on retaining customers, who will return if you can ensure a flawless shopping experience.

About the author:

Yuri Kovalov is CEO of automated load testing platform PFLB.