Micro Frontend Concepts

🧩 Micro Frontends Overview

Micro Frontends is a design pattern where a web application’s frontend is split into smaller, independently developed and deployed modules. Each module (or micro frontend) is responsible for a specific feature or section of the UI, similar to microservices on the backend.

Micro Frontends are an architectural pattern that extends the concepts of microservices to the frontend. It involves breaking down a large, monolithic frontend application into a collection of smaller, more manageable, and independently deployable components called micro frontends. These components are composed into a unified user interface, allowing different teams to work autonomously on separate features, potentially using different technology stacks.

📐 Architecture

• Shell Application: Hosts and orchestrates micro frontends
• Micro Frontend Modules: Self-contained apps for features like search, cart, profile
• Integration Techniques: Module Federation, Web Components, iframes, single-spa

⚛️ Core concepts

Decomposition by feature: Instead of horizontal slicing (e.g., separating by technology layers), a micro frontend architecture is typically organized around business domains or "verticals," where a single team is responsible for a feature end-to-end, from the backend service to the user interface.

Independent teams: Each micro frontend is owned by a small, autonomous team. This enables parallel development, faster feature delivery, and greater ownership.

Composition: A container or shell application is responsible for assembling the various micro frontends into a single, cohesive webpage at runtime.

Technology agnosticism: Different micro frontends can be developed using different frameworks (e.g., React, Vue, Angular), allowing teams to choose the best tool for the job or modernize legacy components incrementally.

🔗 Integration approaches

• 🧩 Client-side integration (Web Components): This approach uses a central shell application to load and mount micro frontends using a standardized browser primitive, the Custom Element. This is highly flexible, and a core concept behind frameworks like Single-SPA.
• 🧩 Client-side integration (Module Federation): Webpack 5's Module Federation allows an application to dynamically load code from another application at runtime, treating it as a dependency. This enables seamless integration of micro frontends and sharing of dependencies.
• 🧩 Server-side composition: Micro frontends are rendered on the server, and the HTML is composed by a central server using templates or fragments.
• 🧩 Iframes: The traditional approach uses iframes to isolate different parts of the application. While providing strong isolation, this method can have drawbacks related to performance and flexibility.

🧪 Example: E-Commerce Platform

• Product Listing: Built with React
• Shopping Cart: Built with Angular
• User Profile: Built with Vue.js
• Shell: Loads and coordinates all modules

✅ Advantages

• 🚀 Independent deployments: Teams can deploy their micro frontend updates without affecting the entire application, which reduces risk and speeds up releases.
• 🤝 Autonomous teams: Breaking down a large codebase allows smaller, cross-functional teams to work independently, reducing bottlenecks and fostering innovation.
• 📈 Scalability: The architecture scales with both the application and the organization. New features can be added by creating new, independent micro frontends.
• 🛠️ Incremental upgrades: A legacy monolithic frontend can be modernized incrementally by replacing parts of it with new micro frontends, avoiding the risk of a full rewrite.
• ⚙️ Technology flexibility: Teams are free to choose the most suitable technology stack for their specific micro frontend, preventing technology lock-in.
• 🧹 Improved maintainability: Smaller, self-contained codebases are easier to understand, test, and maintain.

⚠️ Disadvantages

• ⚙️ Increased complexity: Managing multiple repositories, build pipelines, and deployments adds significant operational complexity.
• 🎨 Consistency challenges: Ensuring a consistent user experience (UI/UX) across different, independently developed micro frontends requires careful planning and a robust design system.
• 🐢 Performance overhead: Without proper optimization (e.g., sharing dependencies), users may end up downloading duplicate framework code, increasing payload size and potentially slowing down the application.
• 🔄 Shared state management: Managing data and communication between different micro frontends can be challenging and requires careful design to avoid tight coupling.
• 🧪 Testing overhead: Integration testing becomes more complex as it requires assembling and testing the different micro frontends together.

🕐 When to use

• 🏢 Large, complex applications: When the application is so large that a monolithic frontend is unmanageable and slows down development.
• 👥 Multiple independent teams: If different teams own and work on distinct features of a single application.
• 🛠️ Legacy modernization: To incrementally migrate a legacy monolith to a more modern architecture without a risky "big bang" rewrite.
• 📆 Independent release cycles: When different parts of the application need to be updated and deployed on their own schedule.

🚫 When not to use

• 🔸 Small or simple applications: The complexity is not justified, and a monolith is a more efficient solution.
• 🔸 Small teams or startups: The overhead of setting up and managing a micro frontend architecture is high and can divert focus from core feature development.
• 🔸 High coordination required: If the application requires a high degree of tight, real-time communication between different parts, a monolithic approach might be simpler.

🛡️ Precautions

• ✂️ Define clear boundaries: Carefully define the boundaries between micro frontends to minimize communication and dependencies. A well-defined API contract is crucial.
• 🎨 Invest in a design system: To maintain a consistent UI/UX, establish a shared design system or component library that all teams must adhere to.
• 📦 Manage shared dependencies: Use tools like Webpack Module Federation or a shared content delivery network (CDN) to manage common dependencies and avoid unnecessary duplication.
• 🤖 Embrace automation: Robust Continuous Integration and Continuous Deployment (CI/CD) pipelines for each micro frontend are essential to make independent deployments feasible.
• ⚖️ Avoid over-fragmentation: Do not create a micro frontend for every tiny component, as this can lead to excessive complexity and minimal value.

💡 Best practices

• 🧱 Start with a monolith: Build a monolithic application first. Once the application and team grow, you can identify clear business domains and gradually refactor them into micro frontends.
• 🌐 Favor native browser features: Use web standards like Custom Events for communication over custom, cross-team APIs to favor simple and robust communication.
• 🔗 Backend for Frontend (BFF) pattern: Consider having a separate backend for each micro frontend to serve its specific needs, which further decouples the frontend from downstream services.
• 📊 Log and monitor: Implement monitoring and logging solutions that provide visibility into the health and performance of each individual micro frontend, making it easier to pinpoint and resolve issues.
• 🧪 Test effectively: Prioritize unit tests within each micro frontend and use a limited number of end-to-end (functional) tests to validate the integration between them.

💡 Tips

• Start with a monolith and extract micro frontends gradually
• Use single-spa or Webpack Module Federation for orchestration
• Document module boundaries and responsibilities

Sources: FreeCodeCamp, DEV Community, GeeksforGeeks