Load vs stress vs soak testing

WHAT THIS TESTS: Whether you understand that performance testing has distinct flavors, each answering a different reliability question.

A GOOD ANSWER COVERS: Load testing applies expected production traffic, including realistic peaks, to verify the system meets its latency and throughput targets under normal conditions. You use it before launch or after changes to confirm SLOs hold at anticipated demand. Stress testing deliberately pushes load past the system's rated capacity to discover the breaking point, how the system fails, and whether it degrades gracefully and recovers afterward. Use it to find limits and validate failure handling and autoscaling. Soak testing, also called endurance testing, runs a sustained, typically moderate load for an extended period, hours or days, to reveal problems that only emerge over time, such as memory leaks, slowly filling disks, connection-pool exhaustion, or cache fragmentation that a brief test never triggers.

COMMON WRONG ANSWERS: Using the three terms interchangeably, assuming a single short load run validates durability, or thinking stress testing is just a bigger load test without focusing on the failure mode.

LIKELY FOLLOW-UPS: How long should a soak test run? How do you find the breaking point safely? What environment should these run in? How do you generate realistic traffic patterns?

ONE CONCRETE EXAMPLE: Before a product launch you run a load test at the projected peak of one thousand requests per second and confirm p99 latency stays within target. You then run a stress test ramping to three thousand requests per second to learn the service tips over around twenty-two hundred, shedding load gracefully and recovering once traffic drops. Finally you run a soak test at six hundred requests per second for twenty-four hours and catch a slow memory leak that would have crashed the service after a few days in production but never showed up in the short load run.