When performing load tests, it can be important to test your website and applications against concurrent users, and in some cases, simultaneous users, but what is the difference? And when should you carry out concurrent vs. simultaneous user testing? A lot of people get confused when they hear the words “concurrent users” and “simultaneous users.” Even the most qualified techies get confused when they talk about concurrent and simultaneous users and related topics. Though there are many different definitions and examples available all over the web, it is likely that either you do not understand them or get more confused after reading them.
When it comes to performance testing, it becomes even more critical that you understand concurrent vs. simultaneous users at the fundamental level to effectively apply your knowledge for successful testing. Performance testing such as load testing, stress testing, etc., are heavily influenced by the type of load and user activities. Without further ado, let us understand it bit by bit. This article sets out to explain the differences between the two terms and provides best practices for each, so you are prepared the next time you load test your website or web application.
Concurrent vs. Simultaneous Users
Concurrent Users
Concurrent users refer to the total number of users actively interacting with a system, application, or website at the same time. These users may not necessarily be performing actions simultaneously but are still logged in and engaging with the system during the same period. For instance, one user might be browsing a product page, while another is adding items to their cart. The concept of concurrent users is important for understanding how a system handles a typical workload and for designing realistic load testing scenarios. By identifying how many users are accessing the system at a given time, teams can simulate these conditions during testing to evaluate performance, resource utilization, and stability under normal or peak loads.
Simultaneous Users
Simultaneous users, on the other hand, are users who perform specific actions at the exact same time within a system or application. For example, a scenario where 100 users all click the “Submit” button on a form at precisely the same moment would involve simultaneous users. This metric is crucial for understanding how a system responds to spikes in activity, such as during flash sales, ticket releases, or any event where multiple users trigger the same action concurrently. Testing with simultaneous users helps uncover potential bottlenecks in processing requests and ensures that the system can handle high-intensity traffic without crashing or slowing down.
Concurrent vs. Simultaneous User Testing
While the terms “concurrent users” and “simultaneous users” are often used interchangeably, they represent different testing scenarios and goals.
Testing with concurrent users focuses on evaluating the system’s ability to handle a steady or expected workload over time. It involves users performing various actions at different times, mimicking real-world usage patterns. This type of testing is valuable for assessing overall performance, resource utilization, and scalability under normal and peak conditions.
In contrast, testing with simultaneous users is about pushing the system to its limits by simulating a high-intensity load where many users perform the same action at the exact same moment. This is ideal for identifying weak points, bottlenecks, or vulnerabilities during sudden traffic surges, helping ensure the system remains stable and responsive under pressure.
By combining both concurrent and simultaneous user testing, teams can gain a comprehensive understanding of how their system performs under real-world conditions and extreme scenarios, ensuring a smooth user experience for all.
Concurrent Users Testing
While doing performance testing for concurrent users, the following are a few things that you should consider while designing your tests:
- Peak Traffic. Number of users that are connected to your website or application.
- Resource Utilization. CPU, Bandwidth, Memory, Server Resources
- Load Time. Website/individual page load time will get affected by concurrent users.
- Soak Testing. Website/application performance over a longer duration of time with same number of concurrent users.
- Third-party APIs. Test any third-party integrations for their load handling capacity.
- Maximum Number of Database Connections. A database connection is required for different activities and transactions. More concurrent users may result in increased database connections, but not always.
- Max HTTP Requests. Your server may be able to handle only so much of all types of HTTP requests.
Simultaneous User Testing
While carrying out performance testing for simultaneous users, the following are a few things that you should consider while designing your tests:
- Page Load Time. Test your individual/important pages for simultaneous requests.
- Critical User Transactions. Important transactions such as sign-in, checkout, add-to-cart, etc. should be tested for simultaneous users.
- Third-party APIs. Test individual third-party transactions such as OTP, payment method, push notifications, etc., for simultaneous requests.
- Database I/O. Test database performance for simultaneous read/write transactions.
Concurrent & Simultaneous User Load Testing
Using a platform like LoadView allows you to generate a fixed and adjustable load for virtually any test case. Before we explain more into how you can use the platform for your concurrent user and simultaneous user load, let us talk about some of the differentiators that make it one of the best load testing platforms. The platform offers some out-of-the-box load testing features that are useful for making test cases for concurrent and simultaneous user testing.
- Website Load Testing. Peak traffic analysis for website load time, and resource utilization.
- Web Page Load Testing. Simultaneous individual page requests for logins, shopping carts, forms, etc.
- API Load Testing. Origin server API and third-party API requests.
- Streaming Media Load Testing. Test streaming server performance for concurrent and simultaneous load.
- Postman Collections. Upload Postman collections to test API performance against real-world traffic conditions.
- JMeter Scripts. Run large-scale performance tests from a fully managed network against your existing JMeter scripts.
Concurrent vs. Simultaneous User Testing
Knowing the difference between concurrent vs. simultaneous users is essential for designing test cases and ensuring the correct outcomes. Concurrent users tell the number of users for a given test duration, while simultaneous users define the number of users performing the same transaction at any given point of time. For more information about how to translate website analytics into concurrent users for performance testing, read out Analytics to Concurrent Users Knowledge Base article.
LoadView is a cloud-based load testing tool that you can use for virtually any test case that involves testing concurrent users and simultaneous users for website and application performance. It can generate load using real browsers and devices from different geo locations for the most realistic test conditions and accurate results.
Try LoadView today and receive up to 5 free load tests to get started. Begin your LoadView trial now!