Chapter 7 — The Scope of Architecture Characteristics

Why it matters

Characteristics don’t apply to “the whole system” uniformly. This chapter gives you the granular unit for reasoning about them.

Core ideas

• Architecture quantum (borrowed from Building Evolutionary Architectures): an independently deployable artifact with high functional cohesion, high static coupling, and synchronous dynamic coupling. In short — a deployable unit that includes everything it needs to function (including, importantly, its own data).
• Static coupling = how services are wired together to operate (dependencies, contracts, infra — the “operational glue”). Dynamic coupling = how services call each other at runtime (synchronous vs. asynchronous communication).
• Why the quantum matters: characteristics can be scoped per quantum, not per system. Two parts of a system can legitimately have different availability or scalability requirements — and that observation is the seed of choosing distributed architectures (esp. microservices).

Trade-offs to argue

A single monolithic quantum forces one set of characteristics on everything (simple but coarse). Multiple quanta let you tune characteristics independently, at the cost of distribution complexity. This chapter is the bridge from Part I into architecture styles.

Terms to own

architecture quantum, static vs. dynamic coupling, independently deployable, functional cohesion at the quantum level.