Micro-Frontends Architecture: Scaling Frontend Teams

When Monoliths Break Down

Micro-frontends apply microservices principles to frontend development. The goal: independent teams that can build, test, and deploy their features without coordinating with other teams.

This is not about technology - it is about organizational scaling. When you have multiple teams contributing to a single frontend, coordination costs grow exponentially. Micro-frontends create clear ownership boundaries that align with team structure.

The Right Conditions

Micro-frontends add complexity. They are worth it when:

Multiple teams (3+) work on the same application

Teams need different deployment cadences

You are migrating from legacy systems incrementally

The application has grown beyond what one team can maintain

Different parts have different technology requirements

They are overkill when you have a small team, a simple application, or when the coordination overhead is manageable.

Integration Approaches

Build-time integration: Package micro-frontends as npm packages, compose at build time. Simplest approach but requires coordinated releases.

Runtime integration via JavaScript: Load micro-frontends as JavaScript bundles at runtime. Module Federation is the modern standard here.

Server-side composition: Compose HTML fragments on the server. Good for SEO-critical pages and progressive enhancement.

Web Components: Encapsulate micro-frontends in custom elements. Framework-agnostic but with some limitations.

Module Federation Deep Dive

Webpack 5's Module Federation enables true runtime integration. Each micro-frontend exposes components, and hosts consume them dynamically. No build-time coordination required.

Key concepts:

Exposes: Components this micro-frontend shares with others

Remotes: Other micro-frontends this one consumes

Shared: Dependencies that should be deduplicated across micro-frontends

Sharing React is critical - multiple React instances cause hooks to break. Mark React and React DOM as singletons with version requirements.

Cross-Cutting Concerns

Some things span micro-frontend boundaries:

Authentication: Shared auth state, usually in the shell

Routing: Coordinated navigation between micro-frontends

Design system: Consistent look and feel across boundaries

Error handling: Global error boundaries and reporting

Analytics: Unified tracking across the application

These typically live in a "shell" application that orchestrates the micro-frontends.

Failure Handling

When a remote micro-frontend fails to load, the entire application should not crash. Implement graceful degradation:

Error boundaries around remote components

Fallback UI for failed loads

Retry logic with exponential backoff

Health checks before routing to micro-frontends

Best Practices

Align with teams: One team, one micro-frontend

Share a design system: Visual consistency across boundaries

Deploy independently: No coordination required

Handle failures gracefully: Resilience at every boundary

Minimize shared state: Communication through well-defined contracts

Invest in developer experience: Local development must be fast