Unlocking the Power of Microfrontends: Single-SPA with Module Federation

In today’s fast-paced development environment, scaling applications efficiently without compromising performance or maintainability is a constant challenge. As microservices revolutionized backend architecture, microfrontends are doing the same for frontend development. But how do we integrate multiple microfrontends seamlessly and ensure efficient code sharing across them? The answer lies in combining two powerful technologies: Single-SPA and Module Federation.

In this article, we’ll explore how the combination of Single-SPA and Module Federation differs from simple Module Federation and why this hybrid approach is a game-changer for building modern web applications.

What is Single-SPA?
Single-SPA (Single Single Page Application) is an open-source JavaScript framework that enables you to build microfrontends. It allows you to combine multiple independent applications or front-end frameworks (React, Angular, Vue, etc.) into a single cohesive app. Each microfrontend runs independently, can be developed and deployed separately, and can be mounted or unmounted dynamically as needed.

Think of it as the conductor of an orchestra — Single-SPA is responsible for managing the lifecycle, routing, and interaction between different parts of the frontend application.

What is Module Federation?
Introduced in Webpack 5, Module Federation enables the sharing of JavaScript modules across applications at runtime. It allows one application (the “host”) to load and run code from another application (the “remote”) without having to bundle everything together at build time. This results in more efficient code management, as shared dependencies can be dynamically loaded when required.

In simpler terms, Module Federation removes the need to duplicate libraries or components in different applications, ensuring that only one instance of a module exists, which optimizes bundle sizes and speeds up load times.

Single-SPA + Module Federation: The Ultimate Synergy
When combined, Single-SPA and Module Federation allow you to orchestrate multiple microfrontends while dynamically sharing code between them. Here’s how the two work together:

1. Single-SPA handles the application lifecycle and routing of each microfrontend, ensuring that they are loaded only when necessary and maintaining a smooth user experience.
2. Module Federation allows these microfrontends to share common modules or dependencies in real time without bundling them separately, reducing duplication and improving performance. This synergy between Single-SPA and Module Federation not only boosts the scalability of your application but also optimizes the overall architecture by allowing teams to work independently and deploy microfrontends in isolation.

Simple Module Federation vs. Single-SPA with Module Federation
While Module Federation alone allows you to share modules between applications, combining it with Single-SPA introduces several powerful enhancements. Let’s explore how they differ:

1. Application Composition
   • Simple Module Federation: In a basic Module Federation setup, a host application loads remote modules at runtime, typically for specific components or features. This is often done in static applications where the microfrontend modules are simply added as needed.
   • Single-SPA with Module Federation: This combination allows dynamic composition of entire microfrontends. Each microfrontend is treated as an independently deployable application, and Single-SPA manages the orchestration, routing, and lifecycle of these apps. The result is a highly modular architecture where each team can manage their own microfrontend.
2. Multi-Framework Support
   • Simple Module Federation: It’s primarily used for sharing modules between applications built with the same framework (e.g., React to React).
   • Single-SPA with Module Federation: One of the biggest advantages of Single-SPA is its ability to integrate microfrontends built with different frameworks (e.g., React, Angular, Vue) into one cohesive application. Module Federation works seamlessly in this setup, ensuring that shared libraries are available to all microfrontends without duplication.
3. Independent Deployment and Versioning
   • Simple Module Federation: You can independently deploy shared modules, but there is no framework for managing the deployment of the entire application.
   • Single-SPA with Module Federation: The combination allows independent deployment of both microfrontends and shared dependencies. Single-SPA controls the loading and unloading of each microfrontend, while Module Federation ensures that only the necessary modules are shared across applications. This setup is perfect for large teams that work on different parts of the application and need to deploy without breaking the overall system.
4. Lifecycle Management
   • Simple Module Federation: Module Federation itself doesn’t manage the lifecycle of applications — it simply shares code between them.
   • Single-SPA with Module Federation: Single-SPA goes beyond code sharing and manages the entire lifecycle of microfrontends. It provides lifecycle hooks like mount, unmount, and update, ensuring smooth transitions between different parts of the app. This means you can easily load/unload microfrontends based on user navigation, reducing the footprint of your app on initial load and improving performance.
5. Complexity and Setup
   • Simple Module Federation: Easier to set up in simpler scenarios where only shared modules are needed, and the overall application structure is less complex.
   • Single-SPA with Module Federation: Requires more initial setup and configuration. You need to configure both Single-SPA for handling routing and lifecycle management, as well as Module Federation for sharing code. This setup is more complex but offers significantly greater flexibility and scalability for larger applications.

Why Combine Single-SPA with Module Federation?
Here are the key benefits of using both technologies together:

• Scalability: You can scale your application by adding more microfrontends as the team grows, while ensuring that shared dependencies are efficiently managed at runtime.
• Code Sharing: Module Federation minimizes duplication of shared libraries like React, Lodash, and more, reducing the overall bundle size.
• Team Autonomy: Different teams can build, deploy, and update their microfrontends independently, speeding up the development cycle and enabling continuous delivery.
• Framework Agnostic: Single-SPA enables you to use different frameworks side-by-side within the same application. Module Federation ensures that these frameworks share their common dependencies seamlessly.
• Optimized Performance: Shared dependencies are loaded only once at runtime, reducing the initial load time and improving overall performance.

Best Practices for Implementing Single-SPA with Module Federation

1. Manage Dependencies Carefully: Ensure that all shared dependencies have compatible versions to avoid runtime conflicts.
2. Optimize Bundles: Use lazy loading to load remote modules only when they are needed. This can significantly reduce the initial load time.
3. Keep Microfrontends Modular: Each microfrontend should have a well-defined responsibility to avoid overlap in functionality.
4. Version Control: Implement a versioning strategy for shared libraries to prevent breaking changes across microfrontends.
5. Monitor Performance: Regularly monitor the performance of your microfrontends to ensure that the integration of multiple technologies doesn’t lead to degradation in user experience.

Conclusion
Combining Single-SPA with Module Federation takes the concept of microfrontends to the next level by enabling dynamic code sharing, framework agnosticism, and seamless lifecycle management. While Module Federation alone is a powerful tool for sharing modules, integrating it with Single-SPA unlocks the full potential of scalable, maintainable, and high-performance web applications.

This approach is especially beneficial for large applications built by distributed teams, where independent development, deployment, and orchestration of microfrontends are crucial. If you’re building a modern web application, adopting Single-SPA with Module Federation could be the key to achieving a flexible, future-proof architecture.