GraphQL vs REST: When to Use Each Technology

The API Landscape

REST dominated for two decades. GraphQL emerged as alternative, solving specific REST limitations. Neither universally better—choose based on use case.

REST Fundamentals

REST uses HTTP methods on resources:

• GET /users (list)
• POST /users (create)
• GET /users/:id (detail)
• PATCH /users/:id (update)
• DELETE /users/:id (delete)

Strengths:

• Simple, stateless
• Cacheable (HTTP caching works)
• Browser-compatible (open URLs)
• Massive ecosystem and knowledge

Weaknesses:

• Over-fetching: GET /users returns all fields, not just needed ones
• Under-fetching: Need multiple requests (user + orders + payments)
• Versioning pain: API changes require new endpoints (/v1/users, /v2/users)

GraphQL Revolution

GraphQL lets clients request exactly what they need:

query {
  user(id: "123") {
    name
    email
    orders {
      id
      total
    }
  }
}

Single query, no over-fetch. Get user + orders in one request.

Strengths:

• Precise data fetching
• Single endpoint
• Type system (schema defines valid queries)
• Excellent for complex, interconnected data
• No versioning: add fields without breaking old clients

Weaknesses:

• Query complexity: badly written queries kill performance
• Caching complexity: HTTP caching doesn't apply
• Learning curve: clients must learn GraphQL
• Backend complexity: implement resolvers for each field
• Subscription complexity: WebSocket management

When REST Makes Sense

Simple APIs: CRUD operations, straightforward data models. REST clarity wins.

Browser clients: Paste URL in address bar? REST works. GraphQL needs POST.

Caching critical: CDNs cache GET requests transparently. GraphQL requires application-level caching.

Public APIs: Consumers expect REST. GraphQL adds friction (new tools, learning curve).

Example: Public weather API. GET /forecast?lat=40&lon=-74. Simple, cacheable, widely understood.

When GraphQL Wins

Complex data graphs: User has orders, orders have items, items have reviews. GraphQL eliminates request waterfall.

Multiple client types: Web app needs full user profile. Mobile app needs only name + avatar. GraphQL clients request differently, single backend serves both.

Rapid development: Adding fields requires no migration. Clients fetch new fields immediately.

Internal APIs: Engineering teams comfortable with GraphQL. Standardizes data access across services.

Example: SaaS dashboard. Users access different data (analytics, billing, settings). GraphQL clients fetch only needed data.

Hybrid Approach

Many successful systems use both:

// REST for simple operations
app.get('/users/:id', async (req, res) => {
  const user = await getUser(req.params.id);
  res.json(user);
});

// GraphQL for complex queries
app.post('/graphql', graphqlHandler);

Public API uses REST (simpler). Internal GraphQL endpoint for web/mobile apps (flexible queries).

Performance Considerations

REST:

• Multiple round trips for related data
• HTTP 2 multiplexing helps but doesn't eliminate waterfall
• Simpler caching

GraphQL:

• Single request even for complex data
• But query parsing and resolving takes time
• Caching harder (field-level caching, dataloaders needed)

At scale, GraphQL performance depends on backend optimization:

// Naive resolver: N+1 query problem
const userResolvers = {
  orders: async (user) => {
    // Executes for each user, could be 1000 queries!
    return db.query('SELECT * FROM orders WHERE user_id = ?', [user.id]);
  }
};

// Optimized with dataloaders: single batch query
const userResolvers = {
  orders: async (user) => {
    return orderLoader.load(user.id);
  }
};

const orderLoader = new DataLoader(async (userIds) => {
  // Single query fetches all orders for all users
  const orders = await db.query(
    'SELECT * FROM orders WHERE user_id IN (?)',
    [userIds]
  );
  return userIds.map(id => orders.filter(o => o.user_id === id));
});

Practical Framework

Choose REST if:

• Simple CRUD operations
• Public API (consumers expect REST)
• Caching is critical
• Team unfamiliar with GraphQL

Choose GraphQL if:

• Complex, interconnected data
• Multiple client types (web, mobile, etc.)
• Rapid feature development
• Internal API (team control)
• Willing to invest in proper implementation

Use both if:

• Public REST API for simplicity
• Internal GraphQL for flexibility
• Reverse proxy routes requests appropriately