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🌟 Architecture Principles

Software architecture is not a collection of individual styles or techniques but is supported by foundational "Principles." This page systematically organizes the major architectural principles that work commonly across styles.

✅ Dependency Direction​

One of the most important principles in architecture is to intentionally design which direction dependencies point.

  • Avoid dependencies from Higher Layers (Policy) → Lower Layers (Detail).
  • Concrete implementations should follow abstract interfaces (DIP: Dependency Inversion Principle).
  • Styles like Hexagonal, Onion, and Clean Architecture place this principle at their core.

Dependency direction directly affects changeability, testability, and modularity.

✅ Coupling & Cohesion​

Key elements of sound design include:

  • Low Coupling: Minimizing dependencies on other components.
  • High Cohesion: A single module has consistent responsibilities.

Coupling and cohesion relate to all structural styles and also influence topologies (Microservices / Modular Monolith).

✅ Boundaries & Context​

In architecture, defining where to draw Boundaries is one of the most critical decisions.

  • Bounded Context
  • Boundary definition via Interfaces / Ports
  • Alignment with team boundaries (Conway's Law)

Boundary design determines the scalability and changeability of the system.

✅ Sync vs Async​

The difference in communication methods affects the entire structure.

  • Synchronous: REST/gRPC, Request-Response type.
  • Asynchronous: Event-driven, Stream processing, Messaging.

Appropriate methods must be selected based on availability, latency, and consistency requirements.

✅ Consistency Models​

Key points in data-centric design:

  • Strong Consistency
  • Eventual Consistency
  • Trade-offs based on scale (CAP / PACELC)

CQRS, Event Sourcing, and Microservices presuppose an understanding of consistency models.

✅ Essential Complexity vs Accidental Complexity​

There are two types of system complexity:

  • Essential Complexity: The complexity inherent in the domain itself.
  • Accidental Complexity: Unnecessary complexity added by technology choices or design.

Excellent architecture reduces accidental complexity and realizes a structure that allows focusing on essential value.

✅ Center of Gravity in Design (Operational / Domain / Data)​

Architecture changes depending on which of the following centers of gravity is prioritized:

  • Operational (Availability, Resilience, Monitoring)
  • Domain (Domain Model Expression)
  • Data (Data-centric, Analytics Workloads)

Where you place the center of gravity naturally leads to style selection and topology.

✅ Summary​

Architecture principles are concepts higher than styles or frameworks, and are universal rules that apply consistently regardless of which style is adopted.

By understanding these principles, you acquire the foundation to assemble design intent according to purpose, rather than just "choosing" individual styles.