Next.js App Router: Best Practices and Patterns

The App Router Paradigm

Next.js App Router represents a fundamental shift in how we build React applications. Understanding its patterns is essential for building modern, performant web applications.

Server Components by Default

Think Server-First

In the App Router, components are Server Components by default. This means:

No JavaScript sent to the client for server components

Direct database access without API routes

Secure handling of sensitive data

Smaller bundle sizes

When to Use Client Components

Add 'use client' only when you need:

Event handlers (onClick, onChange)

Browser APIs (localStorage, geolocation)

React hooks (useState, useEffect)

Third-party client libraries

Data Fetching Patterns

Fetch in Server Components

Fetch data directly in your components:

Parallel data fetching with Promise.all

Automatic request deduplication

Built-in caching and revalidation

Loading States

Use loading.tsx files for streaming UI:

Instant loading states

Progressive page rendering

Better perceived performance

Route Organization

File-Based Routing

Organize routes logically:

Group related routes with (folders)

Use route groups for shared layouts

Implement parallel routes for complex UIs

Catch-all routes for dynamic paths

Caching Strategies

Understanding Next.js Caching

Request Memoization - Dedupe identical requests

Data Cache - Persist fetch results

Full Route Cache - Cache rendered routes

Router Cache - Client-side cache

Revalidation

Time-based revalidation with revalidate

On-demand revalidation with revalidatePath/revalidateTag

Opt out of caching when needed

Error Handling

Graceful Error Boundaries

error.tsx for route-level errors

global-error.tsx for root errors

not-found.tsx for 404 pages

Custom error UI with recovery options

Performance Tips

Use dynamic imports for heavy components

Implement proper image optimization

Leverage edge runtime when appropriate

Monitor bundle sizes with @next/bundle-analyzer