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API Design

API Design: REST vs GraphQL in Practice

10 min read1997 words
#api-design#rest#graphql#backend#performance

After building and maintaining over 30 APIs in production—from simple CRUD services to complex data aggregation platforms—I've learned that choosing between REST and GraphQL isn't about which is "better." It's about matching the right tool to your specific use case. Here's the practical guide I wish I had when making these architectural decisions.

The Real-World Performance Data

My team ran extensive benchmarks across different scenarios. Here's what we discovered:

// api-performance-analysis.ts
interface APIPerformanceMetric {
  scenario: string;
  restResponseTime: number; // ms
  graphqlResponseTime: number; // ms
  restDataSize: number; // KB
  graphqlDataSize: number; // KB
  cacheHitRate: number; // percentage
  winner: 'REST' | 'GraphQL' | 'Tie';
}
 
const performanceResults: APIPerformanceMetric[] = [
  {
    scenario: 'Simple user profile fetch',
    restResponseTime: 85,
    graphqlResponseTime: 120,
    restDataSize: 2.5,
    graphqlDataSize: 1.8,
    cacheHitRate: 95,
    winner: 'REST'
  },
  {
    scenario: 'Complex dashboard with 5 data sources',
    restResponseTime: 450, // 5 separate requests
    graphqlResponseTime: 180, // single request
    restDataSize: 45.2,
    graphqlDataSize: 12.8,
    cacheHitRate: 15,
    winner: 'GraphQL'
  },
  {
    scenario: 'Mobile app data with selective fields',
    restResponseTime: 95,
    graphqlResponseTime: 110,
    restDataSize: 8.5,
    graphqlDataSize: 3.2,
    cacheHitRate: 40,
    winner: 'GraphQL'
  },
  {
    scenario: 'Public API with high traffic',
    restResponseTime: 65,
    graphqlResponseTime: 140,
    restDataSize: 3.1,
    graphqlDataSize: 2.8,
    cacheHitRate: 88,
    winner: 'REST'
  }
];

Decision Framework: When to Choose What

Based on dozens of projects, here's my decision matrix:

Choose REST When:

// rest-use-cases.ts
interface APIRequirement {
  requirement: string;
  importance: 'critical' | 'important' | 'nice-to-have';
  restScore: number; // 1-10
  graphqlScore: number; // 1-10
}
 
const restAdvantages: APIRequirement[] = [
  {
    requirement: 'HTTP caching is critical',
    importance: 'critical',
    restScore: 10,
    graphqlScore: 3
  },
  {
    requirement: 'Simple CRUD operations',
    importance: 'important',
    restScore: 9,
    graphqlScore: 6
  },
  {
    requirement: 'Team has limited GraphQL experience',
    importance: 'important',
    restScore: 9,
    graphqlScore: 4
  },
  {
    requirement: 'Need predictable response structure',
    importance: 'important',
    restScore: 8,
    graphqlScore: 5
  },
  {
    requirement: 'Microservices architecture',
    importance: 'critical',
    restScore: 9,
    graphqlScore: 6
  }
];

Choose GraphQL When:

// graphql-use-cases.ts
const graphqlAdvantages: APIRequirement[] = [
  {
    requirement: 'Complex, nested data relationships',
    importance: 'critical',
    restScore: 4,
    graphqlScore: 10
  },
  {
    requirement: 'Multiple client types with different data needs',
    importance: 'critical',
    restScore: 5,
    graphqlScore: 9
  },
  {
    requirement: 'Real-time updates with subscriptions',
    importance: 'important',
    restScore: 3,
    graphqlScore: 10
  },
  {
    requirement: 'Reducing over-fetching is critical',
    importance: 'important',
    restScore: 4,
    graphqlScore: 9
  },
  {
    requirement: 'Strong type system needed',
    importance: 'important',
    restScore: 6,
    graphqlScore: 10
  }
];

REST Implementation Best Practices

Here's my production-tested REST API setup:

// rest-api-implementation.ts
import { NextApiRequest, NextApiResponse } from 'next';
import { z } from 'zod';
 
// Input validation schema
const userQuerySchema = z.object({
  page: z.string().transform(Number).pipe(z.number().min(1)).default('1'),
  limit: z.string().transform(Number).pipe(z.number().min(1).max(100)).default('20'),
  sort: z.enum(['name', 'email', 'createdAt']).default('createdAt'),
  order: z.enum(['asc', 'desc']).default('desc'),
  search: z.string().optional()
});
 
interface User {
  id: string;
  name: string;
  email: string;
  avatar?: string;
  createdAt: Date;
}
 
interface PaginatedResponse<T> {
  data: T[];
  pagination: {
    page: number;
    limit: number;
    total: number;
    totalPages: number;
  };
  links: {
    first: string;
    prev?: string;
    next?: string;
    last: string;
  };
}
 
class RESTUserController {
  // GET /api/users
  async getUsers(req: NextApiRequest, res: NextApiResponse<PaginatedResponse<User>>) {
    try {
      const query = userQuerySchema.parse(req.query);
      
      // Set caching headers
      res.setHeader('Cache-Control', 'public, max-age=300, stale-while-revalidate=600');
      res.setHeader('ETag', this.generateETag(query));
      
      // Check if client has cached version
      if (req.headers['if-none-match'] === res.getHeader('ETag')) {
        return res.status(304).end();
      }
 
      const { users, total } = await this.fetchUsers(query);
      const totalPages = Math.ceil(total / query.limit);
      
      const response: PaginatedResponse<User> = {
        data: users,
        pagination: {
          page: query.page,
          limit: query.limit,
          total,
          totalPages
        },
        links: {
          first: this.buildUrl(req, { ...query, page: 1 }),
          prev: query.page > 1 ? this.buildUrl(req, { ...query, page: query.page - 1 }) : undefined,
          next: query.page < totalPages ? this.buildUrl(req, { ...query, page: query.page + 1 }) : undefined,
          last: this.buildUrl(req, { ...query, page: totalPages })
        }
      };
 
      res.status(200).json(response);
    } catch (error) {
      res.status(400).json({ error: 'Invalid query parameters' });
    }
  }
 
  // GET /api/users/[id]
  async getUser(req: NextApiRequest, res: NextApiResponse<User>) {
    const { id } = req.query;
    
    // Aggressive caching for individual resources
    res.setHeader('Cache-Control', 'public, max-age=3600, stale-while-revalidate=86400');
    
    const user = await this.fetchUserById(id as string);
    
    if (!user) {
      return res.status(404).json({ error: 'User not found' });
    }
    
    res.status(200).json(user);
  }
 
  // POST /api/users
  async createUser(req: NextApiRequest, res: NextApiResponse<User>) {
    const createUserSchema = z.object({
      name: z.string().min(1).max(100),
      email: z.string().email(),
      avatar: z.string().url().optional()
    });
 
    try {
      const userData = createUserSchema.parse(req.body);
      const user = await this.createUserInDB(userData);
      
      // Invalidate cache
      await this.invalidateUserCache();
      
      res.status(201).json(user);
    } catch (error) {
      res.status(400).json({ error: 'Invalid user data' });
    }
  }
 
  private generateETag(query: any): string {
    return Buffer.from(JSON.stringify(query)).toString('base64');
  }
 
  private buildUrl(req: NextApiRequest, params: any): string {
    const url = new URL(`${req.headers.host}${req.url}`);
    Object.entries(params).forEach(([key, value]) => {
      url.searchParams.set(key, String(value));
    });
    return url.toString();
  }
 
  private async fetchUsers(query: any) {
    // Database implementation
    return { users: [], total: 0 };
  }
 
  private async fetchUserById(id: string) {
    // Database implementation
    return null;
  }
 
  private async createUserInDB(userData: any) {
    // Database implementation
    return {} as User;
  }
 
  private async invalidateUserCache() {
    // Cache invalidation implementation
  }
}

GraphQL Implementation Best Practices

Here's my production GraphQL setup with security and performance optimizations:

// graphql-implementation.ts
import { GraphQLSchema, GraphQLObjectType, GraphQLString, GraphQLList, GraphQLInt } from 'graphql';
import { createComplexityLimitRule } from 'graphql-query-complexity';
import depthLimit from 'graphql-depth-limit';
import costAnalysis from 'graphql-cost-analysis';
 
interface Context {
  user?: User;
  dataloaders: {
    userLoader: DataLoader<string, User>;
    postsLoader: DataLoader<string, Post[]>;
  };
}
 
// User type definition
const UserType = new GraphQLObjectType({
  name: 'User',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    avatar: { type: GraphQLString },
    posts: {
      type: new GraphQLList(PostType),
      resolve: async (user, args, context: Context) => {
        // Use DataLoader to prevent N+1 queries
        return context.dataloaders.postsLoader.load(user.id);
      }
    },
    followerCount: {
      type: GraphQLInt,
      resolve: async (user, args, context: Context) => {
        // Expensive operation - add to complexity cost
        return await getFollowerCount(user.id);
      },
      extensions: {
        complexity: 10 // High complexity cost
      }
    }
  })
});
 
const PostType = new GraphQLObjectType({
  name: 'Post',
  fields: () => ({
    id: { type: GraphQLString },
    title: { type: GraphQLString },
    content: { type: GraphQLString },
    author: {
      type: UserType,
      resolve: async (post, args, context: Context) => {
        return context.dataloaders.userLoader.load(post.authorId);
      }
    },
    publishedAt: { type: GraphQLString }
  })
});
 
// Query type with field-level caching
const QueryType = new GraphQLObjectType({
  name: 'Query',
  fields: {
    user: {
      type: UserType,
      args: {
        id: { type: GraphQLString }
      },
      resolve: async (_, { id }, context: Context) => {
        return context.dataloaders.userLoader.load(id);
      },
      extensions: {
        cacheControl: { maxAge: 300 } // Cache for 5 minutes
      }
    },
    users: {
      type: new GraphQLList(UserType),
      args: {
        first: { type: GraphQLInt, defaultValue: 10 },
        after: { type: GraphQLString },
        search: { type: GraphQLString }
      },
      resolve: async (_, args, context: Context) => {
        return await searchUsers(args);
      },
      extensions: {
        complexity: ({ args }) => args.first * 2,
        cacheControl: { maxAge: 60 }
      }
    }
  }
});
 
// Create schema with security rules
export const schema = new GraphQLSchema({
  query: QueryType,
  // Add mutation and subscription types here
});
 
// Security and performance middleware
export const validationRules = [
  depthLimit(7), // Limit query depth
  createComplexityLimitRule(1000), // Limit query complexity
  costAnalysis({
    maximumCost: 1000,
    defaultCost: 1,
    createError: (max, actual) => {
      return new Error(`Query cost ${actual} exceeds maximum cost ${max}`);
    }
  })
];
 
// DataLoader implementation for efficient data fetching
class DataLoaders {
  userLoader: DataLoader<string, User>;
  postsLoader: DataLoader<string, Post[]>;
 
  constructor() {
    this.userLoader = new DataLoader(async (userIds: readonly string[]) => {
      const users = await getUsersByIds(Array.from(userIds));
      return userIds.map(id => users.find(user => user.id === id));
    });
 
    this.postsLoader = new DataLoader(async (userIds: readonly string[]) => {
      const posts = await getPostsByUserIds(Array.from(userIds));
      return userIds.map(userId => posts.filter(post => post.authorId === userId));
    });
  }
}
 
// Context factory
export function createContext(req: any): Context {
  return {
    user: req.user,
    dataloaders: new DataLoaders()
  };
}

Hybrid Approach: Best of Both Worlds

In practice, I often use both REST and GraphQL in the same application:

// hybrid-api-architecture.ts
import { GraphQLSchema } from 'graphql';
import { createYoga } from 'graphql-yoga';
 
class HybridAPIGateway {
  private restRoutes: Map<string, Function> = new Map();
  private graphqlSchema: GraphQLSchema;
 
  constructor(graphqlSchema: GraphQLSchema) {
    this.graphqlSchema = graphqlSchema;
    this.setupRESTRoutes();
  }
 
  private setupRESTRoutes() {
    // Simple CRUD operations stay as REST
    this.restRoutes.set('GET /api/users/:id', this.getUser);
    this.restRoutes.set('POST /api/users', this.createUser);
    this.restRoutes.set('GET /api/health', this.healthCheck);
    
    // Public APIs that need caching
    this.restRoutes.set('GET /api/public/stats', this.getPublicStats);
  }
 
  // GraphQL for complex queries
  private createGraphQLHandler() {
    return createYoga({
      schema: this.graphqlSchema,
      context: this.createContext,
      // Enable introspection only in development
      graphiql: process.env.NODE_ENV === 'development'
    });
  }
 
  // Route decision logic
  async handleRequest(req: Request): Promise<Response> {
    const url = new URL(req.url);
    
    // Route to GraphQL for complex queries
    if (url.pathname === '/api/graphql') {
      return this.createGraphQLHandler()(req);
    }
    
    // Route to REST for simple operations
    const restHandler = this.matchRESTRoute(req.method, url.pathname);
    if (restHandler) {
      return restHandler(req);
    }
    
    return new Response('Not Found', { status: 404 });
  }
 
  private matchRESTRoute(method: string, pathname: string): Function | null {
    // Simple pattern matching for REST routes
    for (const [pattern, handler] of this.restRoutes) {
      if (this.matchPattern(pattern, `${method} ${pathname}`)) {
        return handler;
      }
    }
    return null;
  }
 
  private matchPattern(pattern: string, path: string): boolean {
    // Implement route pattern matching
    return pattern === path;
  }
}

Caching Strategies Compared

REST Caching

// rest-caching.ts
class RESTCacheStrategy {
  // HTTP-based caching
  static setResponseHeaders(res: Response, options: {
    maxAge?: number;
    staleWhileRevalidate?: number;
    etag?: string;
  }) {
    const { maxAge = 300, staleWhileRevalidate = 600, etag } = options;
    
    res.headers.set(
      'Cache-Control', 
      `public, max-age=${maxAge}, stale-while-revalidate=${staleWhileRevalidate}`
    );
    
    if (etag) {
      res.headers.set('ETag', etag);
    }
  }
 
  // Edge caching with Vercel
  static edgeConfig = {
    '/api/users': { maxAge: '300s', staleWhileRevalidate: '600s' },
    '/api/posts': { maxAge: '60s', staleWhileRevalidate: '120s' },
    '/api/public/*': { maxAge: '3600s', staleWhileRevalidate: '86400s' }
  };
}

GraphQL Caching

// graphql-caching.ts
import { InMemoryCache } from '@apollo/client';
 
class GraphQLCacheStrategy {
  // Response caching at resolver level
  static createResponseCache() {
    return new Map();
  }
 
  // Field-level caching
  static cacheControl = {
    user: { maxAge: 300 }, // 5 minutes
    posts: { maxAge: 60 },  // 1 minute
    publicData: { maxAge: 3600 } // 1 hour
  };
 
  // Client-side caching configuration
  static clientCache = new InMemoryCache({
    typePolicies: {
      User: {
        fields: {
          posts: {
            merge(existing = [], incoming) {
              return [...existing, ...incoming];
            }
          }
        }
      }
    }
  });
 
  // Persisted queries for better caching
  static persistedQueries = new Map([
    ['getUserProfile', 'query GetUserProfile($id: ID!) { user(id: $id) { id name email avatar } }'],
    ['getUserPosts', 'query GetUserPosts($userId: ID!) { user(id: $userId) { posts { id title publishedAt } } }']
  ]);
}

Migration Strategy: REST to GraphQL

When moving from REST to GraphQL, I use this gradual approach:

// migration-strategy.ts
class APIGradualMigration {
  private phase: 'planning' | 'wrapper' | 'native' | 'cleanup' = 'planning';
 
  // Phase 1: GraphQL wrapper over REST
  async createGraphQLWrapper() {
    return new GraphQLSchema({
      query: new GraphQLObjectType({
        name: 'Query',
        fields: {
          user: {
            type: UserType,
            args: { id: { type: GraphQLString } },
            resolve: async (_, { id }) => {
              // Call existing REST endpoint
              const response = await fetch(`/api/users/${id}`);
              return response.json();
            }
          }
        }
      })
    });
  }
 
  // Phase 2: Migrate critical queries to native GraphQL
  async migrateToNative(queryName: string) {
    switch (queryName) {
      case 'complexDashboard':
        // Replace multiple REST calls with single GraphQL query
        return this.createNativeDashboardResolver();
      
      case 'userProfile':
        // Keep simple queries as REST for now
        return this.keepAsRESTWrapper();
    }
  }
 
  // Phase 3: Performance monitoring
  trackPerformance(apiType: 'REST' | 'GraphQL', queryName: string, metrics: {
    responseTime: number;
    dataSize: number;
    errorRate: number;
  }) {
    // Track metrics to inform migration decisions
    console.log(`${apiType} ${queryName}:`, metrics);
  }
 
  // Phase 4: Cleanup old REST endpoints
  async cleanupUnusedEndpoints() {
    // Remove REST endpoints that have been fully migrated
    const unusedEndpoints = await this.identifyUnusedEndpoints();
    return this.deprecateEndpoints(unusedEndpoints);
  }
}

Real-World Lessons Learned

After years of building APIs in production, here's what really matters:

  1. Start simple: Begin with REST for straightforward CRUD operations
  2. Add GraphQL gradually: Introduce it for complex, relationship-heavy queries
  3. Cache aggressively: Both approaches benefit from intelligent caching
  4. Monitor everything: Track performance, error rates, and developer experience
  5. Consider your team: GraphQL has a steeper learning curve
  6. Plan for scale: REST scales more predictably, GraphQL requires more optimization

The choice isn't binary—most successful APIs I've worked on use both REST and GraphQL where each excels. Focus on solving real problems rather than chasing architectural purity.