API performance testing goes far beyond simply checking if an endpoint responds as expected. It’s about understanding how your system behaves under different levels of load, pressure, and usage patterns. If your APIs are critical to business operations — especially in real-time or high-demand applications — performance testing is a must. It helps ensure your infrastructure is ready for production traffic.
At VersaQA, we mainly carry out performance tests using k6 and JMeter.
Let us now explore different types of Performance testing.
Load testing simulates the expected number of users or API calls your system will handle during normal operations. The goal is to measure response time, throughput, and resource usage as the system runs under realistic demand. This type of testing helps establish a performance baseline. It tells you how well your APIs perform when everything is 'business as usual'. It also helps uncover bottlenecks, such as slow database queries.
Stress testing intentionally pushes your APIs beyond their normal capacity to find the system’s breaking point. This helps you determine how your application behaves under extreme conditions, like a sudden flood of users or a misconfigured client spamming requests. The goal isn’t just to crash the system. Rather, it’s to observe HOW and WHEN it fails and recovers.
Spike testing is a type of stress testing where the load jumps very sharply in a very short time. The point is to simulate a real-world events like flash sales, viral traffic, or some sort of unexpected public exposure.
Soak testing simulates a consistent load over an extended period of time (it can often last many hours, sometimes even days). It helps identify issues like memory leaks, database connection exhaustion, or gradual performance degradation that only appear over long periods of time. This kind of testing is mostly needed for APIs that are meant to support continuous background activity or the ones that are expected to run non-stop. It ensures that your backend remains stable and consistent well beyond initial deployment.
