Hexagonal Architecture — also known as the Ports and Adapters pattern — is a software design approach created by Alistair Cockburn. Its goal is to decouple the core business logic from external systems such as databases, APIs, frameworks, and user interfaces.
By isolating the application core behind “ports” and interacting with the outside world through “adapters,” systems become more maintainable, testable, and flexible to change.
Hexagonal Architecture is built around a few foundational ideas.
Contains business logic and rules
Independent of frameworks, databases, and infrastructure
Represents the heart of the system
Abstract boundaries defining what the application needs or exposes
Describe interactions such as persistence, messaging, external services, and user interfaces
Typically implemented as interfaces or contracts
Concrete implementations that connect ports to real systems, such as:
Database repositories
REST controllers
Message consumers
CLI or UI layers
Can be swapped or replaced without modifying business logic
Inside → Core domain logic
Outside → Infrastructure and external concerns
This separation ensures technology becomes optional rather than structural.
Here’s how the pattern operates in practice:
The application core exposes ports.
These ports define how the outside world can interact with the system.
External systems plug in via adapters.
Each adapter implements a port contract. Examples include:
A REST API adapter that handles HTTP requests
A database adapter that implements persistence logic
A queue adapter that listens to messages
All communication flows through ports.
No external code directly touches business logic.
Adapters can be swapped with minimal effort.
For example:
Replacing SQL with NoSQL
Switching message broker tools
Adding a new UI without rewriting core logic
The architecture promotes inversion of dependencies: the domain does not depend on infrastructure — instead, infrastructure depends on the domain.
High testability — business logic can be tested without databases or frameworks
Strong separation of concerns — core logic stays clean and independent
Technology flexibility — tools and integrations can be replaced more easily
Supports long-term maintainability and refactoring
Well-suited to microservices, event-driven systems, and modern architectural styles
Adds complexity for small or simple projects
Requires design discipline and understanding of boundaries
Can introduce extra boilerplate such as interfaces and adapters
Not a solution to poor design by itself — it is only a structural pattern
Hexagonal Architecture is most valuable in systems that are expected to evolve or grow over time.
Hexagonal Architecture (Ports and Adapters) is a design pattern that separates business logic from external systems using well-defined ports and pluggable adapters. It leads to cleaner, modular, and more testable applications while providing flexibility and technology independence.
However, it also introduces extra structure and complexity, which means it delivers the most benefit in medium-to-large, long-lived systems rather than small or short-lived applications.