Reliability is a measure of how consistently a system performs according to specification or requirements. The measure of reliability is not the same as performance. A reliable system is one that performs at the same level as the stresses on that system change. For example, if the simplest request takes 10ms to complete with one user, the system would be considered reliable if the same request takes 10ms with 1,000,000 concurrent users. The measure of reliability can take many different forms and can be as broad as supporting a certain number of registered users or as specific as requiring the round trip time for a single method invocation to be within a discrete range. The most reliable system is one where a request can be entirely handled in a single process.