lcbp3/specs/99-archives/skills-backup/next-best-practices-original/runtime-selection.md

Runtime Selection

Use Node.js Runtime by Default

Use the default Node.js runtime for new routes and pages. Only use Edge runtime if the project already uses it or there's a specific requirement.

// Good: Default - no runtime config needed (uses Node.js)
export default function Page() { ... }

// Caution: Only if already used in project or specifically required
export const runtime = 'edge'

When to Use Each

Node.js Runtime (Default)

• Full Node.js API support
• File system access (fs)
• Full crypto support
• Database connections
• Most npm packages work

Edge Runtime

• Only for specific edge-location latency requirements
• Limited API (no fs, limited crypto)
• Smaller cold start
• Geographic distribution needs

Detection

Before adding runtime = 'edge', check:

1. Does the project already use Edge runtime?
2. Is there a specific latency requirement?
3. Are all dependencies Edge-compatible?

If unsure, use Node.js runtime.