A System of Architectural Patterns for Scalable, Consistent and Highly Available Multi-Tier Service-Oriented Infrastructures

Service-oriented architectures have become prevalent in enterprise information systems. The underlying infrastructure is typically architected with multiple tiers in order to separate the different concerns such as interface, business logic and data. Modern information systems have strict availability and scalability requirements. The main technique to attain these properties is replication. However, system architects are confronted with a complex environment in which they have to decide which tier(s) to replicate and how. The architectural choice can have great implications for the degree of scalability and availability that can actually be achieved. Furthermore, maintaining consistency is affected by the way the system is replicated. In this chapter, we survey the state of the art in this area and digest it in the form of a system of architectural patterns that will guide system architects and practitioners in evaluating and selecting the appropriate architectural choices to attain a highly available, consistent and scalable service-oriented infrastructure.