Common Performance and Load Issues, or Why Performance Testing for Websites Matters

Performance testing is the process of evaluating how a website or application behaves under expected and peak load conditions. It detects issues like slow page loads, server crashes during traffic spikes, and memory leaks before they affect real users. Companies run performance tests before major releases, marketing campaigns, and system integrations to prevent downtime and revenue loss.

Performance and load testing are a key part of delivering a great user experience. A fast, stable product is what makes people satisfied enough to buy, use, and recommend it to others. Below, we break down the most common performance and load issues – and why every QA team should be catching them early.

Updated: June 2026

What Is Performance Testing in Software?

Performance testing is a type of testing that allows checking the overall behavior of a product (PC software, mobile applications, websites, emulators, simulators) under a certain workload. QA engineers apply performance testing services to estimate the following parameters:

1. Response capacity – the speed of reaction to end-users’ actions/requests.
2. Sensitivity – the analysis of unmeasured underlying continuous variables and connected with the parameters.
3. Permanence – the stability of a product under test.
4. Scalability – the minimum and maximum of your product’s technical possibilities.
5. Reliability – product functioning under specific conditions and during certain periods.

All of the performance tests deliver valuable data for product improvement. But for this, a QA team should initially discuss the parameters they will use to estimate product performance with the development and product management teams. These parameters should include an average number of users, hits per second, errors per second, response time, latency, connect time, throughput, etc.

Key Benefits of Website Performance Testing

Websites that pass regular performance testing load faster, handle traffic spikes without downtime, and deliver consistent user experience across devices. For e-commerce sites, a 1-second improvement in load time can increase conversions by up to 7%. For SaaS platforms, stable performance under peak load directly reduces churn. For any business with an online presence, performance testing is the difference between retaining users and losing them to a competitor who loads faster.

Now, when to run performance testing? The checkups are a must after every big update of the product and before integrating other systems or databases into the functionality.

Big marketing campaigns are one more reason to check the performance of a website or an app once more. For example, Black Friday, Cyber Monday, and holiday discounts attract many more shoppers than usual.

The same happens when a company announces the release of a major update – users rush in to check it out. Therefore, it is essential to make sure that a product can handle intense user flow. As for running regression tests after every code change, it may be resource-consuming while not necessary.

Common Performance Testing Issues

Performance testing issues, being a part of the fast-changing and sometimes unpredictable IT world, substantially evolve along with the technologies. Users have become more demanding during recent years.

Let’s say, a decade ago, both the selection of e-commerce stores and their technical capabilities were lower than today. Back then, customers could have agreed to wait 10 seconds for a web page to load, but not a few minutes. People would use a new app just because it is one of a kind, but not if it drains the battery and causes extreme heating of a device.

Nowadays, if it takes more than three seconds for a page to load, customers will most likely abandon it and look for a site that works faster. They would also uninstall an app only a few minutes after installing it if this app is buggy. Users still look for new and functional solutions and still prefer fast performance. The standards and demands, however, have evolved.

Based on our experience in the QA, the most frequently detected performance issues fall into several categories.

Threading Issues

It is important to achieve the highest level of concurrent execution in developed product performance. You may be surprised, but not only insufficient threading is a problem; extreme threading is a performance issue as well. The other common defects are thread blockage and thread waiting lines.

Memory Issues

Issues with optimization of memory usage encompass incorrect caching, object sizes, memory allocation of new objects, removing unnecessary objects, etc. Memory management principles explain all of the memory potential issues.

Algorithmic Defects

Here we are dealing with the basics – exactness and optimization of product logic. Logic issues, also known as algorithmic, reveal gaps in logic.

Server Response Time & Page Loading Time

As you already know, users are rather impatient nowadays. They aren’t ready to wait too long for a page to respond and content to load. Both types of issues may be the result of unoptimized scripts, an abundance of plugins, improper caching, or web hosting specifications.

Website Outages

You’ve probably noticed that some websites go down due to the intense user flow. It happened to Disney+ on its launch day, to Xbox on Series X launch day, and to thousands of other well-known and not so much web resources. To prevent such crashes, QA specialists run spike tests, checking how a system handles traffic spikes.

Accumulating In-App Data

As you make progress in a game or complete more levels in an educational app, it becomes heavier. The app stores more data now and, thus, occupies more space. The same happens as streaming apps start caching multimedia content or when you save something to offline mode. It can result in increased CPU usage and slow response. Such issues are a task for volume tests – one more type of performance testing.

Configuration Bugs

Configuration testing checks the effect of newly added software configurations to ensure uninterrupted and accurate functioning. For example, a money manager app that generates reports in a column chart and a pie chart is supposed to use the same time for processing and the same hardware resources. These different configurations that shouldn’t affect the performance.

A Mixture of Several Issues

Different performance issues can mix unexpectedly. The classic example is a general slow application performance related to the slow performance of some smallest component. Joined by an incorrect adjustment of configuration elements, gaps in logic or any other minor issue can result in a considerable slowdown.

What Is Load Testing And When To Run It?

The name says it all. Load testing checks the maximal system potential under real-life based load conditions: simultaneous users, multiplex operations, an extended period of functioning, different network conditions, etc.

Load testing is a type of performance testing, but many QA specialists prefer to distinguish it as an independent one (probably, because load tests are run the most frequently compared to other types).

Why is load testing crucial? Business websites and applications should ensure uninterrupted running to support seamless flow of the related processes. It is especially significant under peak user load: during reporting periods, credit card billing, regular payment procedures, etc.).

For an e-commerce store, a possibility to handle an intense user flow directly affects the profit. And speaking about healthcare software, outages can be a threat to people’s health and lives.

Also, competition is getting fierce as more new software solutions appear on the market. To attract loyal users, you should make sure that your product performs well. Otherwise, they would start looking for faster and better functioning solutions.

A performance testing strategy should include several types of potential load scenarios for different system parts to detect the weak and strong sides of a product.

To Wrap Up

The modern IT industry is becoming more challenging and competitive. The final product should bring the maximum possible benefits to end-users. Hence, it’s better to conduct performance testing before the product goes live. No business aims to receive negative reviews, a low number of downloads, and sales underperformance.

Checking at least server response & page loading time, CPU resources usage, and an ability to handle traffic spikes is a usual task for every QA company. Still, even covering the basic aspects of software performance will prevent the majority of issues that leave users irritated and looking for better solutions.

FAQ

What is performance testing in software?

Performance testing is a type of software testing that checks how a system behaves under a specific workload. It measures response time, stability, scalability, and resource usage to ensure the product performs reliably for real users.

Why does performance testing matter for websites?

Websites that fail performance testing load slowly, crash during traffic spikes, and lose users to faster competitors. Performance testing identifies these issues before they reach production, protecting revenue and user experience.

What are the most common performance testing issues?

The most common issues include threading problems, memory leaks, algorithmic defects, slow server response times, website outages under traffic spikes, accumulating in-app data, and configuration bugs.

When should you run performance testing?

Performance testing should be run after every major product update, before integrating new systems or databases, and ahead of high-traffic events like marketing campaigns, product launches, or seasonal sales.