The Service-Based Abstract Style, introduced in the previous chapter, offers many Above Average and High capabilities balanced against manageable cost and complexity. The capabilities afforded by the defining constraints of that style will satisfy all but the most extreme demands. However, there do exist systems where anything less than extreme agility, extreme scalability, and extreme fault tolerance poses an existential threat. Achieving such extremes is not easy and requires a similarly demanding set of architectural constraints to maximize the capabilities of the system.