For years, layered architecture was the default choice for building enterprise software. It’s familiar: controllers call services, services call repositories, and the database sits at the bottom. But a quiet shift is happening—senior engineers are increasingly choosing hexagonal architecture (also called Ports and Adapters) for modern applications.
What’s Wrong With Layered Architecture?
- Tight Coupling: Business logic depends directly on frameworks and databases.
- Difficult Testing: Mocking dependencies across layers becomes painful.
- Rigid Boundaries: Changing a data source or delivery method often breaks multiple layers.
The Hexagonal Approach
Hexagonal architecture flips the model:
- Core Domain Logic in the Center – Your business rules live independently.
- Ports and Adapters Around It – Frameworks, UIs, and databases become interchangeable adapters.
- Dependency Inversion – The core doesn’t depend on external tools; external tools depend on the core.
Why Senior Engineers Favor It
- Testability: You can test business logic without touching databases or UIs.
- Flexibility: Swap a database, messaging queue, or API without rewriting the core.
- Future-Proofing: As technologies evolve, adapters can change without disturbing core logic.
- Cleaner Boundaries: Encourages good design practices and maintainability.
A Practical Example
Imagine you start with MySQL but later need PostgreSQL or a cloud datastore. In layered architecture, that migration might touch every layer. In hexagonal design, you replace one adapter—your domain logic stays untouched.
When Not to Use It
Hexagonal architecture adds complexity. For small, short-lived projects, a layered approach may still be simpler and faster.
Key Takeaway
Senior engineers prefer hexagonal architecture because it isolates business logic, improves testability, and makes applications more adaptable to change—qualities that matter as systems scale and evolve.
