Layered Architecture vs Hexagonal Architecture: Structuring Business Logic

Tue, 04 Aug 2026 05:08:09 +0900

Overview

Layered Architecture stacks an application into horizontal layers, where each layer may only call the one directly beneath it. Hexagonal Architecture instead puts business logic at the center and connects it to the outside world through ports and adapters, so no top-to-bottom hierarchy exists at all. The distinction matters because it determines how easily you can swap infrastructure, test in isolation, and keep framework details from leaking into core logic.

Comparison Diagram

Comparison Table

Aspect	Layered Architecture	Hexagonal Architecture
Structural organization	Horizontal layers (presentation, business, persistence); each layer only calls the one below it	Concentric layout with a domain core surrounded by ports and adapters; no top/bottom hierarchy
Dependency direction	Strictly downward: layer N depends only on layer N-1	Always inward: adapters depend on the core, the core depends on nothing external
Entry and exit points	Requests enter at the presentation layer and exit at the database layer	Requests enter through any driving port and exit through any driven port
Business logic isolation	Business layer is often still coupled to persistence details that leak upward	Domain core is fully isolated behind port interfaces and unaware of any adapter
Swapping infrastructure	Replacing a database or UI framework often requires touching multiple layers	Swapping an adapter (e.g., DB for an in-memory store) requires no changes to the core
Testing strategy	Unit tests typically mock the layer directly beneath the one under test	Core logic is tested directly through ports; adapters are tested separately
Common pitfall	“Layered lasagna”: persistence concerns bleed upward into the business layer	Over-engineering ports and adapters for simple CRUD apps adds needless indirection
Best fit	Traditional CRUD apps with a straightforward request/response flow	Domain-heavy apps needing multiple interfaces (REST, CLI, events) or high testability

Key Differences

Layered enforces dependency in one direction (top-down) while hexagonal enforces dependency inward toward the domain core.
Hexagonal defines explicit ports as boundaries; layered relies on looser, implicit layer contracts.
Layered architecture is simpler to learn but prone to leaky abstractions between layers.
Hexagonal architecture makes it trivial to swap infrastructure without touching business logic.

When to Use Each

Layered Architecture

Hexagonal-Architecture on IT Comparison

Layered Architecture vs Hexagonal Architecture: Structuring Business Logic

Overview

Comparison Diagram

Comparison Table

Key Differences

When to Use Each