Capacity Testing
Capacity testing determines the maximum load a system can handle — users, transactions, or data volume — while still meeting its defined performance requirements, establishing the ceiling a system can be scaled up to before it needs additional infrastructure.
Where load testing checks behavior at an expected traffic level, capacity testing pushes further, deliberately increasing load until performance requirements are no longer met, to find the actual maximum the current infrastructure can sustain — a number needed for capacity planning, not just performance validation.
The result feeds directly into infrastructure decisions: knowing a system's real capacity ceiling (say, 5,000 concurrent users before response times degrade past an acceptable threshold) tells a team exactly when they need to scale, well before that ceiling is hit unexpectedly during a real traffic spike.
