Understanding Clean Architecture: Principles, Layers, and Practical Reflections

In a recent internal sharing session the author discussed his understanding of software architecture, but the original presentation was rushed and vague; this post reorganizes that material, adds missing details, and aims to inspire readers.

Target audience : the article is suitable for intermediate to senior engineers who are interested in improving architectural design.

Background story : a teammate ("Xiao Wang") asked how to lower the difficulty of modifying business code through architecture, providing a link to a lengthy Go implementation of Clean Architecture. The author spent several nights studying that blog and extracting its core ideas.

Clean Architecture overview : the model consists of concentric circles where inner layers define rules (entities, use cases) and outer layers provide implementations (interface adapters, frameworks & drivers). The further a layer is from the center, the more concrete it becomes.

The architecture emphasizes several characteristics:

Framework‑independence – the design does not rely on any specific framework.

Testability of business rules – logic can be tested without UI, database, or external services.

Implementation‑agnostic functionality – the same backend can serve web apps or native apps.

Database‑agnostic business logic – the core does not change when swapping databases such as Oracle, MySQL, MongoDB, etc.

Overall, business logic remains untouched regardless of external changes.

Dependency rule : only outer layers may depend on inner layers; inner layers must never know about outer ones. Data flow follows the same direction – outer layers may accept data structures defined by inner layers, but not vice‑versa.

Key terminology :

Entities – encapsulate enterprise‑wide business rules.

Use Cases – encapsulate application‑specific rules.

Interface Adapters – convert data between inner layers and external formats (e.g., database records, UI models).

Frameworks & Drivers – concrete tools and libraries such as web frameworks or ORM drivers.

The number of layers can be adjusted to fit project size; the essential idea is the layered thinking and strict dependency direction.

Inversion of Control (IoC) : to let outer code call inner code while preserving the dependency rule, inner layers define interfaces that outer layers implement, a pattern similar to the Factory Method or Abstract Factory and applicable in many languages, not just Go.

Re‑evaluating the existing architecture : after analysis the author concluded that the current MVC‑style architecture already meets the project’s needs; refactoring to Clean Architecture would not reduce development effort for the given scope, and would add unnecessary complexity.

What architecture means :

Architecture is born from business needs.

It focuses on decoupling.

It facilitates communication and collaboration.

It must evolve over time.

Effective architecture requires deep business understanding, modular decomposition, clear boundaries, and thorough documentation to support future changes.

Becoming an architect : developers should gain practical experience, master the details of their tech stack, and continuously study business domains; starting with small‑scale designs builds confidence before tackling larger systems.

Domain‑Driven Design (DDD) is highlighted as a practical methodology that emphasizes focusing on the domain model and iterative development with close collaboration between developers and domain experts.

Personal conclusion : the author reflects on a lifelong commitment to learning, acknowledges the value of the Clean Architecture concepts introduced, and sets a future goal to continue advancing toward higher‑level architectural challenges.