rest-to-graphql-migrator

REST to GraphQL Migrator

Incrementally migrate REST APIs to GraphQL without breaking existing clients.

Core Workflow

1. Analyze REST endpoints: Document existing API
2. Design GraphQL schema: Map REST to types
3. Create REST data source: Wrap existing endpoints
4. Implement resolvers: Connect to REST
5. Migrate incrementally: One endpoint at a time
6. Deprecate REST: Gradual sunset

Migration Strategies

Strategy Comparison

REST Data Source Wrapper

Apollo RESTDataSource

// datasources/users.datasource.ts
import { RESTDataSource } from '@apollo/datasource-rest';

export class UsersAPI extends RESTDataSource {
  override baseURL = process.env.REST_API_URL;

  // Add auth header
  override willSendRequest(_path: string, request: AugmentedRequest) {
    request.headers['Authorization'] = this.context.token;
  }

  // GET /api/users
  async getUsers(params?: { page?: number; limit?: number }) {
    const query = new URLSearchParams();
    if (params?.page) query.set('page', String(params.page));
    if (params?.limit) query.set('limit', String(params.limit));

    return this.get<User[]>(`/api/users?${query}`);
  }

  // GET /api/users/:id
  async getUser(id: string) {
    return this.get<User>(`/api/users/${id}`);
  }

  // POST /api/users
  async createUser(input: CreateUserInput) {
    return this.post<User>('/api/users', { body: input });
  }

  // PATCH /api/users/:id
  async updateUser(id: string, input: UpdateUserInput) {
    return this.patch<User>(`/api/users/${id}`, { body: input });
  }

  // DELETE /api/users/:id
  async deleteUser(id: string) {
    await this.delete(`/api/users/${id}`);
    return true;
  }

  // GET /api/users/:id/posts
  async getUserPosts(userId: string) {
    return this.get<Post[]>(`/api/users/${userId}/posts`);
  }
}