Micro-frontend architecture

// shell/src/app.routes.ts
import { Routes } from '@angular/router'; // or React Router / Vue Router equivalent
import { loadRemoteModule } from '@module-federation/enhanced/runtime';

export const routes: Routes = [
  {
    path: 'dashboard',
    loadComponent: () => loadRemoteModule({
      remote: 'dashboardApp',
      exposedModule: './Dashboard'
    }).then(m => m.default)
  },
  {
    path: 'settings',
    loadComponent: () => loadRemoteModule({
      remote: 'settingsApp',
      exposedModule: './Settings'
    }).then(m => m.default)
  }
];

// shell/webpack.config.js
const { ModuleFederationPlugin } = require('webpack').container;

module.exports = {
  plugins: [
    new ModuleFederationPlugin({
      name: 'shell',
      remotes: {
        dashboardApp: 'dashboardApp@http://localhost:3001/remoteEntry.js',
        settingsApp: 'settingsApp@http://localhost:3002/remoteEntry.js'
      },
      shared: {
        react: { singleton: true, requiredVersion: '^18.2.0' },
        'react-dom': { singleton: true, requiredVersion: '^18.2.0' },
        '@shared/ui': { singleton: true, requiredVersion: '^1.0.0' }
      }
    })
  ]
};

ep 3: Configure Remote Applications Each remote exposes specific entry points and declares its own shared dependencies. The exposes field defines the public API contract.

// dashboardApp/webpack.config.js
const { ModuleFederationPlugin } = require('webpack').container;

module.exports = {
  plugins: [
    new ModuleFederationPlugin({
      name: 'dashboardApp',
      filename: 'remoteEntry.js',
      exposes: {
        './Dashboard': './src/Dashboard.tsx'
      },
      shared: {
        react: { singleton: true, requiredVersion: '^18.2.0' },
        'react-dom': { singleton: true, requiredVersion: '^18.2.0' }
      }
    })
  ]
};

Step 4: Implement Explicit Contracts

Micro-frontends must communicate through typed interfaces, not shared global state. Define contracts in a shared package or inline.

// contracts/src/dashboard.types.ts
export interface DashboardProps {
  userId: string;
  theme: 'light' | 'dark';
  onNavigate: (path: string) => void;
}

export interface DashboardWidget {
  id: string;
  title: string;
  component: React.ComponentType<{ data: unknown }>;
}

// dashboardApp/src/Dashboard.tsx
import React from 'react';
import type { DashboardProps, DashboardWidget } from '@contracts/dashboard.types';

export const Dashboard: React.FC<DashboardProps> = ({ userId, theme, onNavigate }) => {
  // Implementation isolated to this remote
  return (
    <section data-remote="dashboardApp">
      <h1>Dashboard</h1>
      <button onClick={() => onNavigate('/settings')}>Go to Settings</button>
    </section>
  );
};

export default Dashboard;

Step 5: Handle Shared Dependencies & Version Negotiation

Module Federation resolves shared dependencies at runtime. If the shell provides react@18.2.0 and the remote requests ^18.0.0, the shell's version is used. Mismatched major versions trigger fallback loading. Always pin peer dependencies and use semantic version ranges in shared config.

Step 6: Implement CSS Isolation

Style leakage is the most common production failure. Use one of three strategies:

1. CSS Modules / Scoped Styles: Automatic class name hashing.
2. Shadow DOM: True encapsulation, but requires careful event retargeting.
3. Namespace Prefixing: data-remote="dashboardApp" selectors with strict specificity rules.

/* dashboardApp/styles.css */
[data-remote="dashboardApp"] .widget {
  /* isolated styles */
}

Step 7: Error Boundaries & Fallbacks

Remote loading can fail. Wrap remote mounts in error boundaries.

import React, { Suspense, ErrorBoundary } from 'react';

export const RemoteWrapper: React.FC<{ fallback: React.ReactNode; children: React.ReactNode }> = ({ fallback, children }) => (
  <ErrorBoundary fallback={<div>Module failed to load</div>}>
    <Suspense fallback={fallback}>
      {children}
    </Suspense>
  </ErrorBoundary>
);

Pitfall Guide

1. Over-sharing dependencies: Declaring every library as shared: true forces version alignment across teams, creating merge bottlenecks. Only share core runtime libraries (React, Vue, Angular, router, state manager). Let remotes bundle their own utilities.

2. Tight coupling via global state: Sharing Redux stores, Vuex, or NgRx across remotes defeats deployment independence. Use explicit prop passing, custom event buses, or lightweight cross-app communication via window.postMessage or WebSockets for cross-cutting concerns.

3. Ignoring CSS isolation: Without scoping, z-index conflicts, specificity wars, and reset style collisions break layouts. Enforce a naming convention or adopt Shadow DOM for critical UI boundaries. Audit styles in CI with stylelint rules targeting remote prefixes.

4. Neglecting error boundaries & fallbacks: A failed remote module can crash the entire shell. Always wrap loadRemoteModule calls in Suspense + ErrorBoundary. Implement retry logic with exponential backoff for network failures.

5. Treating it as a component library: Micro-frontends are deployable applications, not UI primitives. Components belong in shared design systems. Micro-frontends own routing, state, and business logic for their domain. Mixing the two creates architectural ambiguity.

6. Skipping versioning strategy: Breaking changes in exposed modules propagate instantly to all consumers. Implement contract versioning (./Dashboard/v1) and deprecation policies. Use semantic versioning in shared config and enforce it in CI.

7. Performance blindness: Multiple remote entries, waterfall requests, and redundant runtime loaders increase TTI. Implement route-based prefetching, bundle analysis per remote, and performance budgets. Cache remoteEntry.js aggressively with immutable headers.

Production Bundle

Action Checklist

• Define explicit TypeScript contracts for all exposed modules and cross-app communication
• Configure shared dependencies with strict version ranges and singleton enforcement
• Implement CSS isolation strategy (modules, shadow DOM, or namespace prefixing)
• Wrap all remote mounts in ErrorBoundary + Suspense with fallback UI
• Set up CI pipeline to validate remoteEntry.js availability and contract compatibility
• Establish performance budgets per remote (max 150KB gzipped, TTI < 1.2s)
• Document deprecation policy for exposed modules and shared dependency upgrades

Decision Matrix

Scenario	Recommended Approach	Why	Cost Impact
Startup scaling from 2 to 5 teams	Build-time MFE (CI composition)	Lower runtime complexity, faster initial setup, easier debugging	Low infrastructure cost, moderate CI maintenance
Enterprise legacy migration with 8+ teams	Runtime MFE (Module Federation)	Enables incremental adoption, independent deploys, framework heterogeneity	Higher runtime overhead, requires contract governance
Multi-vendor ecosystem with external partners	Runtime MFE + CDN-hosted remotes	Strict isolation, version pinning, no shared build pipeline	CDN costs, strict SLA monitoring required

Configuration Template

// webpack.config.js (Standard Production Setup)
const { ModuleFederationPlugin } = require('webpack').container;
const path = require('path');

module.exports = {
  mode: 'production',
  entry: './src/index.ts',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].[contenthash].js',
    publicPath: 'auto'
  },
  plugins: [
    new ModuleFederationPlugin({
      name: 'host',
      remotes: {
        remoteApp: 'remoteApp@https://cdn.example.com/remoteApp/remoteEntry.js'
      },
      exposes: {
        './HostLayout': './src/layouts/HostLayout.tsx'
      },
      shared: {
        react: { singleton: true, requiredVersion: '^18.2.0' },
        'react-dom': { singleton: true, requiredVersion: '^18.2.0' },
        'react-router-dom': { singleton: true, requiredVersion: '^6.0.0' }
      }
    })
  ],
  optimization: {
    splitChunks: {
      chunks: 'all',
      cacheGroups: {
        vendor: {
          test: /[\\/]node_modules[\\/]/,
          name: 'vendors',
          chunks: 'all'
        }
      }
    }
  },
  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: 'ts-loader',
        exclude: /node_modules/
      },
      {
        test: /\.css$/,
        use: ['style-loader', 'css-modules-loader']
      }
    ]
  }
};

Quick Start Guide

1. Initialize shell and remote: Run npx create-mf-app@latest shell and npx create-mf-app@latest remote (select TypeScript + React).
2. Configure remotes: Update shell/webpack.config.js to point to http://localhost:3001/remoteEntry.js and expose ./App in the remote config.
3. Define contract: Create shared/contracts.ts with interface RemoteProps { title: string; } and import in both shell and remote.
4. Mount remote: In shell/src/App.tsx, use loadRemoteModule inside a route or component wrapper with Suspense fallback.
5. Run: Execute npm run start in both directories. The shell loads the remote at runtime. Verify network tab shows single remoteEntry.js fetch and zero duplicate React bundles.