API Versioning Strategy

Table of Contents

• [Overview](#overview)
• [When to Use](#when-to-use)
• [Quick Start](#quick-start)
• [Reference Guides](#reference-guides)
• [Best Practices](#best-practices)

Overview

Comprehensive guide to API versioning approaches, deprecation strategies, backward compatibility techniques, and migration planning for REST APIs, GraphQL, and gRPC services.

When to Use

• Designing new APIs with versioning from the start
• Adding breaking changes to existing APIs
• Deprecating old API versions
• Planning API migrations
• Ensuring backward compatibility
• Managing multiple API versions simultaneously
• Creating API documentation for different versions
• Implementing API version routing

Quick Start

Minimal working example:

// express-router.ts
import express from "express";

const app = express();

// Version 1
app.get("/api/v1/users", (req, res) => {
  res.json({
    users: [{ id: 1, name: "John Doe" }],
  });
});

// Version 2 - Added email field
app.get("/api/v2/users", (req, res) => {
  res.json({
    users: [{ id: 1, name: "John Doe", email: "[email protected]" }],
  });
});

// Shared logic with version-specific transformations
app.get("/api/:version/users/:id", async (req, res) => {
  const user = await userService.findById(req.params.id);

  if (req.params.version === "v1") {
    res.json({ id: user.id, name: user.name });
// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Best Practices

✅ DO

• Version from day one (even if v1)
• Document breaking vs non-breaking changes
• Provide clear migration guides with code examples
• Use semantic versioning principles
• Give 6-12 months deprecation notice
• Monitor usage of deprecated APIs
• Send deprecation warnings to API consumers
• Support at least 2 versions simultaneously
• Use adapters/transformers for version logic
• Test all supported versions
• Log which API version is being used
• Provide migration tooling when possible
• Be consistent with versioning approach

❌ DON'T

• Change API behavior without versioning
• Remove versions without notice
• Support too many versions (>3)
• Use different versioning strategies in same API
• Break APIs without incrementing version
• Forget to update documentation
• Deprecate too quickly (<6 months)
• Ignore feedback from API consumers
• Make every change a new version
• Use version numbers inconsistently