GraphQL & gRPC

1// ============================================
2// GraphQL & gRPC — Comparison with REST
3// ============================================
4
5// ---------- The Over-Fetching Problem (REST) ----------
6
7// REST: Fetch user profile page data
8// Need: user name, avatar, last 5 posts, and follower count
9
10// Request 1: Get user
11// GET /api/v1/users/123
12// Returns ALL 20 fields: id, name, email, phone, address, bio, avatar, ...
13// You only need: name, avatar ← REST returns everything
14
15// Request 2: Get user's posts
16// GET /api/v1/users/123/posts?limit=5
17// Returns ALL post fields: id, content, media, tags, likes, comments, ...
18// You only need: title, preview ← Over-fetching again
19
20// Request 3: Get follower count
21// GET /api/v1/users/123/followers/count
22// Separate request just for a number ← Under-fetching problem
23
24// Total: 3 HTTP requests, 90% of data downloaded is unused!
25
26// ---------- GraphQL Solution ----------
27
28// ONE request to /graphql with exactly what you need:
29const graphqlQuery = `
30  query UserProfile($userId: ID!) {
31    user(id: $userId) {
32      name
33      avatar
34      followerCount
35      posts(limit: 5) {
36        title
37        preview
38        createdAt
39      }
40    }
41  }
42`;
43
44// Server implementation (Node.js + Apollo):
45const { ApolloServer, gql } = require('apollo-server');
46
47const typeDefs = gql`
48  type User {
49    id: ID!
50    name: String!
51    email: String!
52    avatar: String
53    followerCount: Int!
54    posts(limit: Int = 10): [Post!]!
55  }
56
57  type Post {
58    id: ID!
59    title: String!
60    content: String!
61    preview: String!
62    author: User!
63    createdAt: String!
64    likes: Int!
65  }
66
67  type Query {
68    user(id: ID!): User
69    users(limit: Int, cursor: String): UserConnection!
70  }
71
72  type Mutation {
73    createPost(input: CreatePostInput!): Post!
74    updateUser(id: ID!, input: UpdateUserInput!): User!
75  }
76
77  input CreatePostInput {
78    title: String!
79    content: String!
80  }
81
82  input UpdateUserInput {
83    name: String
84    avatar: String
85  }
86
87  type UserConnection {
88    edges: [User!]!
89    pageInfo: PageInfo!
90  }
91
92  type PageInfo {
93    hasNextPage: Boolean!
94    endCursor: String
95  }
96`;
97
98const resolvers = {
99  Query: {
100    user: async (_, { id }) => {
101      return await db.findUser(id);
102    },
103    users: async (_, { limit = 20, cursor }) => {
104      return await db.listUsers(limit, cursor);
105    },
106  },
107  User: {
108    // Field-level resolver — only runs if client requests this field
109    posts: async (user, { limit }) => {
110      return await db.getPostsByUser(user.id, limit);
111    },
112    followerCount: async (user) => {
113      return await db.countFollowers(user.id);
114    },
115  },
116  Mutation: {
117    createPost: async (_, { input }, context) => {
118      if (!context.user) throw new Error('Not authenticated');
119      return await db.createPost(context.user.id, input);
120    },
121  },
122};
123
124// ---------- gRPC Service Definition (.proto) ----------
125
126// user_service.proto
127const protoDefinition = `
128syntax = "proto3";
129
130package userservice;
131
132// Service definition
133service UserService {
134  // Unary RPC (request-response)
135  rpc GetUser (GetUserRequest) returns (User);
136  rpc CreateUser (CreateUserRequest) returns (User);
137
138  // Server streaming (server sends multiple responses)
139  rpc ListUsers (ListUsersRequest) returns (stream User);
140
141  // Client streaming (client sends multiple requests)
142  rpc BatchCreateUsers (stream CreateUserRequest) returns (BatchResult);
143
144  // Bidirectional streaming
145  rpc Chat (stream ChatMessage) returns (stream ChatMessage);
146}
147
148// Message definitions
149message User {
150  int64 id = 1;
151  string name = 2;
152  string email = 3;
153  string avatar = 4;
154  int64 created_at = 5;
155}
156
157message GetUserRequest {
158  int64 id = 1;
159}
160
161message CreateUserRequest {
162  string name = 1;
163  string email = 2;
164}
165
166message ListUsersRequest {
167  int32 limit = 1;
168  string cursor = 2;
169}
170
171message BatchResult {
172  int32 created = 1;
173  int32 failed = 2;
174}
175
176message ChatMessage {
177  string user_id = 1;
178  string content = 2;
179  int64 timestamp = 3;
180}
181`;
182
183// gRPC Node.js Client usage (auto-generated from .proto):
184const grpc = require('@grpc/grpc-js');
185const protoLoader = require('@grpc/proto-loader');
186
187async function grpcClientExample() {
188  // Load proto file (auto-generates typed client)
189  const packageDef = protoLoader.loadSync('user_service.proto');
190  const userProto = grpc.loadPackageDefinition(packageDef).userservice;
191
192  // Create client
193  const client = new userProto.UserService(
194    'localhost:50051',
195    grpc.credentials.createInsecure()
196  );
197
198  // Unary call (like REST GET)
199  client.GetUser({ id: 123 }, (err, user) => {
200    console.log('gRPC response:', user); // Binary → auto-decoded
201  });
202
203  // Server streaming (like SSE)
204  const stream = client.ListUsers({ limit: 100 });
205  stream.on('data', (user) => console.log('Got user:', user.name));
206  stream.on('end', () => console.log('Stream complete'));
207}
208
209// ---------- When to Use What — Decision Matrix ----------
210
211const decisionMatrix = {
212  'Public API (web/mobile clients)': 'REST or GraphQL',
213  'Internal microservices': 'gRPC',
214  'Mobile app with complex data needs': 'GraphQL',
215  'Simple CRUD API': 'REST',
216  'Real-time streaming between services': 'gRPC (bidirectional streaming)',
217  'Third-party developer API': 'REST (universally understood)',
218  'Browser-to-server real-time': 'WebSocket (not gRPC — browser support limited)',
219};
220
221console.log('API Decision Matrix:', decisionMatrix);