Hexagonal architecture
Hexagonal architecture is a software architecture pattern that isolates an application’s core logic from external systems through ports and adapters.
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Hexagonal architecture is an architectural pattern that isolates an application’s core business logic from external systems through ports and adapters.
- How it is used
- Separates an IT asset management domain from REST and persistence integrations while documenting the resulting design.
- How deep it goes
- Defines domain models, primary and secondary ports, and adapters, then applies them in a Python project layout without implementation internals.
- Examples
- Uses an IT asset management system with Hardware, FastAPI, SQLAlchemy, Mermaid class diagrams, package structure, and tests.
- What you can do after
- Evaluate/understand how ports and adapters let external databases, screens, and services change without changing core business logic.
Learn Go with Pocket-Sized Projects
Hexagonal architecture is a software architecture pattern that isolates core application logic from external systems through defined interfaces.
- How it is used
- Separates service logic from HTTP, storage, and gRPC concerns through domain types and adapter boundaries.
- How deep it goes
- Works through package boundaries and conversions, but leaves the small game service short of fully independent layers.
- Examples
- Uses a game service’s session-to-HTTP conversion and a habits service’s protobuf-to-domain client wrapper.
- What you can do after
- Apply it in Go by defining domain-facing types, isolating transport conversions, and testing adapters with mocks.
Read how Learn Go with Pocket-Sized Projects explains hexagonal architecture →
Unit Testing Principles, Practices, and Patterns
An architectural pattern that separates domain logic from application services and connects external applications through ports or common interfaces.
- How it is used
- Structures applications so domain logic stays central while application services orchestrate use cases and external communication.
- How deep it goes
- Defines two layers, dependency direction, and interface boundaries, then demonstrates them through a purchase orchestration example.
- Examples
- Uses user renaming, customer purchasing, repositories, a store interface, and an email gateway as concrete artifacts.
- What you can do after
- Evaluate application boundaries and diagnose fragile tests by distinguishing external behavior from internal communication.
Read how Unit Testing Principles, Practices, and Patterns explains hexagonal architecture →
Go in Action, Second Edition
Ports and Adapters is an architectural pattern that isolates core application logic behind interfaces and connects those interfaces to external implementations.
- How it is used
- Separates a news application's domain logic from RSS, storage, and service infrastructure.
- How deep it goes
- Defines ports and adapters, then works through an RSS adapter's type conversion and compile-time interface check.
- Examples
- Illustrates a gofeed-backed RSS reader, domain feed and article types, and a worker that fetches and stores articles.
- What you can do after
- Build it from scratch by defining domain ports, implementing an RSS adapter, and wiring a worker through interfaces.
Read how Go in Action, Second Edition explains hexagonal architecture →
gRPC Microservices in Go
Hexagonal architecture is an architectural pattern that isolates application business logic behind ports and connects external actors and dependencies through adapters.
- How it is used
- Structures Go microservices around an isolated business-logic core connected to callers and dependencies through ports and adapters.
- How deep it goes
- Defines the pattern and its components, then works through project folders and a Go application core with an injected database port.
- Examples
- Uses a Go order service whose PlaceOrder method saves an Order through DBPort, alongside gRPC adapter and project-folder examples.
- What you can do after
- Build it from scratch by defining the application core and port contracts, then injecting concrete adapters into outer layers.
Read how gRPC Microservices in Go explains hexagonal architecture →
The Art of Unit Testing 3e
An architectural pattern that isolates application logic behind ports and connects it to external systems through replaceable adapters.
- How it is used
- Protects application code and tests from breaking changes in third-party dependencies by routing them through controlled abstractions.
- How deep it goes
- Explains the dependency-boundary rationale and demonstrates injection, but stops short of a broader architectural implementation.
- Examples
- Uses moment.js around password verification and Winston logging as concrete cases for adapters and dependency isolation.
- What you can do after
- Build it from scratch by placing replaceable dependencies behind small internal APIs and injecting fakes at test boundaries.
Read how The Art of Unit Testing 3e explains hexagonal architecture →
Related concepts
- functional, stateless philosophyincludes · Functional programming is a programming paradigm that expresses computation through the evaluation and composition of functions, typically favoring immutable data and minimizing mutable state and side effects.
- portuses · A port is a defined interface or endpoint through which a system communicates with another component, service, or external capability.
- adapteruses · The adapter pattern is a structural design pattern in which a component translates between interfaces or representations so otherwise incompatible components can work together.
- domain layerhas part · A domain layer is an architectural part of an application that contains its domain concepts, rules, and behavior.
- model architecturekind of · The structural organization of a computational system’s components, relationships, and operations that determines how it processes information or behaves.
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