rootcastleco Next.js Best Practices
Principles for Next.js App Router development.
1. Server vs Client Components
Decision Tree
Does it need...?
│
├── useState, useEffect, event handlers
│ └── Client Component ('use client')
│
├── Direct data fetching, no interactivity
│ └── Server Component (default)
│
└── Both?
└── Split: Server parent + Client child
By Default
| Type | Use |
|---|---|
| Server | Data fetching, layout, static content |
| Client | Forms, buttons, interactive UI |
2. Data Fetching Patterns
Fetch Strategy
| Pattern | Use |
|---|---|
| Default | Static (cached at build) |
| Revalidate | ISR (time-based refresh) |
| No-store | Dynamic (every request) |
Data Flow
| Source | Pattern |
|---|---|
| Database | Server Component fetch |
| API | fetch with caching |
| User input | Client state + server action |
3. Routing Principles
File Conventions
| File | Purpose |
|---|---|
page.tsx |
Route UI |
layout.tsx |
Shared layout |
loading.tsx |
Loading state |
error.tsx |
Error boundary |
not-found.tsx |
404 page |
Route Organization
| Pattern | Use |
|---|---|
Route groups (name) |
Organize without URL |
Parallel routes @slot |
Multiple same-level pages |
Intercepting (.) |
Modal overlays |
4. API Routes
Route Handlers
| Method | Use |
|---|---|
| GET | Read data |
| POST | Create data |
| PUT/PATCH | Update data |
| DELETE | Remove data |
Best Practices
- Validate input with Zod
- Return proper status codes
- Handle errors gracefully
- Use Edge runtime when possible
5. Performance Principles
Image Optimization
- Use next/image component
- Set priority for above-fold
- Provide blur placeholder
- Use responsive sizes
Bundle Optimization
- Dynamic imports for heavy components
- Route-based code splitting (automatic)
- Analyze with bundle analyzer
6. Metadata
Static vs Dynamic
| Type | Use |
|---|---|
| Static export | Fixed metadata |
| generateMetadata | Dynamic per-route |
Essential Tags
- title (50-60 chars)
- description (150-160 chars)
- Open Graph images
- Canonical URL
7. Caching Strategy
Cache Layers
| Layer | Control |
|---|---|
| Request | fetch options |
| Data | revalidate/tags |
| Full route | route config |
Revalidation
| Method | Use |
|---|---|
| Time-based | revalidate: 60 |
| On-demand | revalidatePath/Tag |
| No cache | no-store |
8. Server Actions
Use Cases
- Form submissions
- Data mutations
- Revalidation triggers
Best Practices
- Mark with 'use server'
- Validate all inputs
- Return typed responses
- Handle errors
9. Anti-Patterns
| ❌ Don't | ✅ Do |
|---|---|
| 'use client' everywhere | Server by default |
| Fetch in client components | Fetch in server |
| Skip loading states | Use loading.tsx |
| Ignore error boundaries | Use error.tsx |
| Large client bundles | Dynamic imports |
10. Project Structure
app/
├── (marketing)/ # Route group
│ └── page.tsx
├── (dashboard)/
│ ├── layout.tsx # Dashboard layout
│ └── page.tsx
├── api/
│ └── [resource]/
│ └── route.ts
└── components/
└── ui/
Remember: Server Components are the default for a reason. Start there, add client only when needed.
When to Use
This skill is applicable to execute the workflow or actions described in the overview.
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