Have you noticed the term “load testing” getting thrown around by engineering and development teams at your company lately? Or maybe you sometimes chat with these teams about load testing — some of them might mention they need better tools or would like to see company-wide testing. But do you know why these teams perform load testing and the benefits it brings to your organization? If not, this article answers these questions and explains why load testing is crucial for your engineering operation and your business.
Load testing assesses the performance and reliability of a system, such as an application, API, or website, under load. APIs, applications, and software perform differently under load, and many issues will only arise under a specific load level.
An application performs differently under distinct types of traffic. You should never assume your app will perform the same when supporting 10 or 100 users vs. 1k, 5k users, or beyond.
Load testing simulates real traffic to your system to assess its performance, helping you detect and prevent potential problems before they happen.
When we say load testing, we mean testing your system using modern tools and practices, moving away from legacy testing solutions. Modern load testing benefits your organization in many ways:
Your organization needs to adapt to a new world of frequent releases, adopting modern development practices, such as agile DevOps, and continuous integration and continuous delivery (CI/CD). And when you integrate load testing with continuous and automated testing processes, you can avoid software regressions and release higher quality production versions even faster.
Why? Because automated load testing in the CI/CD process allows you to:
When you put these together, you get a culture of velocity and experimentation with a process that boosts efficiency and quality.
Teams with fully automated pipelines were 7x more likely to rate test coverage as good or excellent per Mabl’s “The State of Testing in DevOps in 2022” Survey Report.“
Test automation brought an increase in test coverage, quality improvements, and faster releases for more than 50% of the teams that responded to Capgemini’s “World Quality Report 2022-23.”
Typically, you’ll want to change or scale a particular infrastructure component.
Why? To prepare for a growing demand or because your existing infrastructure is undersized.
Infrastructure in phase A will not be enough for Infrastructure in phase B of the business. For example, Netflix started with a monolithic architecture, but later moved to a microservices architecture to accommodate rapid user growth — the company currently has 231 million paid memberships. Netflix does a lot of testing to ensure the speed and reliability of its platform as the business grows, including load and stress tests.
Too many companies wait to do load testing until they suffer problems due to growth. You should assess infrastructure changes with A/B tests that include load tests. An infrastructure change could be:
Your organization can load test to check the scalability of the old component vs. the new component. The goal is to assess the performance, reliability, and scalability of the new or updated infrastructure to satisfy future demand.
The k6 team recently ran a reverse load test to assess our new infrastructure. (We finished migrating to Kubernetes.) Read this blog post to find out how that test worked out for us.
Load testing helps you prevent software regressions, uncovering issues before they happen.
Why? Because you often only see an issue arise with an API, application, or software under a certain load.
For example, fuboTV, a sports-focused live TV streaming service, might only see the platform slow down or experience errors during huge events with millions of users on the platform at once or thousands signing up for the service at the last minute before a major event. An API could fail or a new feature added to the platform might cause issues with video streaming only under the high load.
With proper load testing, you can:
“Having the confidence that we’ve prevented performance regressions enables us to safely release new features faster, creating more value for our users and gaining an edge over our competitors.”
- Anton Khabaiev, Director of Engineering at fuboTV (To learn more, read the fuboTV case study.)
The best way to reduce the cost of application failure is to catch and fix defects early in the software development life cycle (SDLC).
Why? Because preventing defects often costs far less than reacting to issues caused by defects.
Kent Beck, a well-known software engineer and author, said in "Extreme Programming Explained: Embrace Change":
“Most defects end up costing more than it would have cost to prevent them. Defects are expensive when they occur, both the direct costs of fixing the defects and the indirect costs because of damaged relationships, lost business, and lost development time.”
Load testing gives you the means to minimize the cost of:
Load testing helps you prevent problems or failures that you would have to react to later at a potentially high cost. You can also minimize the cost of failure by reducing the mean time to repair (MTTR) with effective testing and full-stack visibility.
A recent Mabl survey found that teams with good or excellent test coverage are about 3X as likely to resolve bugs within 24 hours compared to those with poor test coverage.
Spike testing is a type of load test that helps you better handle sudden changes in demand or upcoming peak events.
Why? Because you can prepare your applications and systems based on past experiences or estimations.
For example, if your online electronics store crashed on Cyber Monday last year because it saw a 50% spike in shoppers, you can perform load testing to ensure it won’t crash again under the same load or an even higher traffic load.
Load testing helps you:
Always prepare your websites, applications, APIs, or systems to handle major upcoming events and unexpected spikes in demand by performing load testing.
“Our usage of k6 has played a critical role in helping us to push our system to its limits, identify its breaking points, and explore how it would behave in unexpected circumstances.”
- Justin Rusbatch, Staff Software Engineer at Olo (To learn more, read the Olo case study.)
Load testing helps you deliver an excellent user experience.
Why? Because when you load test, you make sure the experience for users is:
Fast. Savvy customers expect your website to be fast and may take their business to competitors if they experience slow-performing pages.
Error-free. If users experience glitches or errors, they may post about their negative experiences on public forums like social media and customer review websites.
Positive. Many factors can lead to a negative user experience — slowness, errors, etc. Load testing helps you ensure users have positive experiences when using your applications.
Users expect a great experience from every site and application they visit. If they have poor experiences on your app or website, they will not sign up or may go with the competition. A best-in-class user experience is critical to the success of your business.
Teams with high test coverage are 1.6x more likely to report high customer happiness than those with little to no test coverage, according to Mabl’s “The State of Testing in DevOps in 2022” Survey Report.
SLAs play an integral part in the success of your business, and load testing allows you to proactively test service level objectives (SLOs) to ensure you meet SLAs.
Why? Because SLAs outline the needs of your users or customers, and load testing helps confirm those needs are met. Companies create SLOs for a range of metrics, including:
Teams usually use tools to monitor SLOs during production and receive alerts when issues could lead to potential breaches. To mitigate this risk and avoid alert fatigue, you need to proactively test your SLOs in pre-production environments to detect potential problems long before they could breach any of your SLOs.
The second most important value that QA brings to the organization is the “reliability of products and services,” according to the Capgemini “World Quality Report 2022-23” report.
You need modern load testing if your company builds software, APIs, or applications — or all of the above. But more than that, you should encourage teams across your organization to get involved in testing. More people in the testing process means you will get more reliable, high-performing products. When your products work well, your users will respond well, which is good for your business and the entire organization.
Looking for an open source tool to implement load testing across your organization? Check out Grafana k6, a developer-friendly and extensible load testing tool for engineering teams.