Performance tests are not only an important instrument for understanding a system and its runtime environment. It is also essential in order to check stability and scalability – non-functional requirements that might be decisive for success. But won't my cloud hosting service scale for me as long as I can afford it? Yes, but… It only operates and scales resources. It won't automatically make your system fast, stable and scalable. This talk shows how such and comparable questions can be clarified with performance tests and how DevOps teams benefit from regular test practise.