Jesse's Notes

Vertical Slice Architecture

2 min read

Vertical Slice Architecture (also called Feature-First Structure) organizes code by features or use cases rather than technical layers.

Core Concept

Instead of organizing by technical concerns (Controllers, Services, Repositories), organize by features or slices that represent complete user workflows.

Traditional Layered vs. Vertical Slice

Traditional Layered

src/
├─ controllers/
│  ├─ UserController.cs
│  └─ OrderController.cs
├─ services/
│  ├─ UserService.cs
│  └─ OrderService.cs
└─ repositories/
   ├─ UserRepository.cs
   └─ OrderRepository.cs

Vertical Slice

src/
├─ features/
│  ├─ users/
│  │  ├─ CreateUser/
│  │  │  ├─ CreateUserRequest.cs
│  │  │  ├─ CreateUserHandler.cs
│  │  │  └─ CreateUserValidator.cs
│  │  └─ GetUser/
│  │     ├─ GetUserRequest.cs
│  │     └─ GetUserHandler.cs
│  └─ orders/
│     └─ PlaceOrder/
│        ├─ PlaceOrderRequest.cs
│        └─ PlaceOrderHandler.cs

Benefits

Cohesion

  • Related code lives together
  • Easy to find all code for a feature
  • Reduces cognitive load

Independent Evolution

  • Features can evolve independently
  • Different features can use different patterns
  • No forced consistency across unrelated features

Team Scaling

  • Teams can own entire features
  • Reduces merge conflicts
  • Clear boundaries for parallel work

Deletion

  • Removing a feature means deleting a folder
  • No scattered code across layers

Principles

CQRS-Friendly

  • Commands and queries are separate slices
  • Each slice optimized for its specific needs
  • No forced abstraction for different operations

Minimal Coupling

  • Slices are independent
  • Shared code extracted only when truly reusable
  • Duplication preferred over wrong abstraction

Feature-Driven

  • Aligns with how users think about the application
  • Maps to user stories and use cases
  • Business-focused organization

Tradeoffs

Advantages:

  • High cohesion within features
  • Easy to understand and navigate
  • Flexible - different slices can use different approaches

Disadvantages:

  • May lead to some code duplication
  • Shared infrastructure needs careful management
  • Less enforcement of consistency

Resources

Graph View

Backlinks