API Versioning Strategy

Choose and implement API versioning approaches with proper deprecation timelines.

Versioning Methods

Method	Example	Pros	Cons
URL Path	/api/v1/users	Clear, cache-friendly	URL clutter
Header	API-Version: 1	Clean URLs	Hidden, harder to test
Query	?version=1	Easy to use	Not RESTful

URL Path Versioning (Recommended)

const v1Router = require('./routes/v1');
const v2Router = require('./routes/v2');

app.use('/api/v1', v1Router);
app.use('/api/v2', v2Router);

Version Adapter Pattern

// Transform between versions
const v1ToV2 = (v1Response) => ({
  data: {
    type: 'user',
    id: v1Response.user_id,
    attributes: {
      name: v1Response.user_name,
      email: v1Response.email
    }
  }
});

Deprecation Headers

app.use('/api/v1', (req, res, next) => {
  res.setHeader('Deprecation', 'true');
  res.setHeader('Sunset', 'Sat, 01 Jun 2025 00:00:00 GMT');
  res.setHeader('Link', '</api/v2>; rel="successor-version"');
  next();
});

Safe vs Breaking Changes

Safe Changes (no version bump):

• Adding optional fields
• Adding new endpoints
• Adding optional parameters

Breaking Changes (requires new version):

• Removing fields
• Changing field types
• Restructuring responses
• Removing endpoints

Deprecation Timeline

Phase	Duration	Actions
Deprecated	3 months	Add headers, docs
Sunset Announced	3 months	Email users
Read-Only	1 month	Disable writes
Shutdown	-	Return 410 Gone

Best Practices

• Support N-1 versions minimum
• Provide 6+ months migration window
• Include migration guides with code examples
• Monitor version usage to inform deprecation