Leveraging Vertical Slice Architecture with Clean Architecture for Scalable, Maintainable Systems

Introduction

As software projects grow, the need for maintainability and modularity becomes even more critical. Recently, I decided to integrate Vertical Slice Architecture into my Ecommerce Microservices solution. My goal was to organize the codebase around business use cases, making it more intuitive and scalable. In this article, I’ll walk you through my thought process, the decisions I made, and why I think this hybrid approach can boost both scalability and productivity.

What is Vertical Slice Architecture?

At its core, Vertical Slice Architecture is all about organizing your code around features or use cases. Instead of dividing the codebase by technical layers (like UI, business logic, and data access), each feature becomes a self-contained unit that houses everything it needs to execute its functionality. This is different from traditional layered architectures, which separate concerns into distinct layers.

clean architecture vertical slice

Why Combine Vertical Slices with Clean Architecture?

While Clean Architecture is great at separating concerns through technical layers, Vertical Slice Architecture focuses on organizing code around real-world business use cases. Combining these two approaches offers several key advantages:

When to choose which and when to combine?

Choosing between Vertical Slice and Clean Architecture really comes down to the needs of your project.

Use Vertical Slice When:

You’re working on a larger, more complex system that needs to stand the test of time. Clean Architecture is ideal for projects where long-term scalability, maintainability, and clear separation of concerns are key.

Opt for Clean Architecture When:

Long-term maintainability and scalability are crucial. Clean Architecture works well for large-scale systems that require strict separation of concerns and stability over time.

Combine Both When:

You want the best of both worlds. If you’re building something large but need to keep development quick and feature-focused, a hybrid approach offers flexibility without sacrificing structure or scalability.

My Implementation

Here’s how I applied his hybrid approach to my solution:

Application Project Reorganization

The Application project is now organized by features, with each feature folder containing:

For example:

Catalog Application Vertical Slice

This structure makes it easy for developers to focus on a single feature at a time, simplifying development and testing.

API Project Reorganization

The API project mirrors the Application project, with feature-based folders. Each folder contains a controller managing a single endpoint. This keeps everything consistent and organized, making it easier to navigate the codebase.

For example:

Catalog API Vertical Slice

Controllers vs. Minimal APIs

I briefly considered using Minimal APIs for defining endpoints but ended up sticking with controllers for now for the following reasons:

While the third reason was the main deciding factor, I’m still open to using Minimal APIs for new services or features moving forward.

Outcome and Benefits

Implementing this hybrid approach can result in several positive outcomes:

Potential Challenges and Solutions

Integrating Vertical Slice Architecture with Clean Architecture does come with some challenges:

Migration Efforts

Transitioning from a traditional layered architecture to a feature-based structure requires careful planning and effort, especially in large-scale systems. It can take time to restructure the codebase around business use cases.

Solution: Start by migrating one or two features at a time, which allows you to test the approach while minimizing disruption.

Code Duplication

Similar logic might emerge across different slices, especially for validation, data access, and business logic. This can complicate maintenance and lead to unnecessary redundancy.

Solution: Create shared services or libraries for common functions like validation and logging, which can be injected across different slices. This keeps the system modular while avoiding duplication.

Cross-Cutting Concerns

Managing concerns like logging, caching, and validation consistently across different slices can be challenging. Without proper planning, each feature may implement these concerns differently, leading to fragmentation.

Solution: Implement middleware or use aspect-oriented programming to handle cross-cutting concerns in a centralized and consistent way.

Conclusion

Integrating Vertical Slice Architecture into Clean Architecture has simplified feature development, making it easier to align with real-world business scenarios and scale the system efficiently. By combining the strengths of both approaches, we can achieve the best of both worlds—rapid feature development and long-term maintainability.

The decision of when to choose Vertical Slice, Clean Architecture, or a hybrid approach depends on your project’s needs. Whether you’re focused on speed, long-term scalability, or a balance of both, understanding when and how to combine these architectures can lead to a more organized, modular, and scalable system.

Ultimately, there’s no one-size-fits-all solution. The key is to adapt your architecture to the unique challenges and goals of your project.

References