apollo-server-patterns

# Apollo Server Patterns

Master Apollo Server for building production-ready GraphQL APIs with proper
schema design, efficient resolvers, and scalable architecture.

## Overview

Apollo Server is a spec-compliant GraphQL server that works with any GraphQL
schema. It provides features like schema stitching, federation, data sources,
and built-in monitoring for production GraphQL APIs.

## Installation and Setup

### Installing Apollo Server

```bash
# For Express
npm install @apollo/server graphql express cors body-parser

# For standalone server
npm install @apollo/server graphql

# Additional utilities
npm install graphql-tag dataloader
```

### Basic Server Setup

```javascript
// server.js
import { ApolloServer } from '@apollo/server';
import { startStandaloneServer } from '@apollo/server/standalone';
import { typeDefs } from './schema.js';
import { resolvers } from './resolvers.js';

const server = new ApolloServer({
  typeDefs,
  resolvers,
  formatError: (formattedError, error) => {
    // Custom error formatting
    if (formattedError.extensions?.code === 'INTERNAL_SERVER_ERROR') {
      return {
        ...formattedError,
        message: 'An internal error occurred'
      };
    }
    return formattedError;
  },
  plugins: [
    {
      async requestDidStart() {
        return {
          async willSendResponse({ response }) {
            console.log('Response sent');
          }
        };
      }
    }
  ]
});

const { url } = await startStandaloneServer(server, {
  listen: { port: 4000 },
  context: async ({ req }) => {
    const token = req.headers.authorization || '';
    const user = await getUserFromToken(token);
    return { user };
  }
});

console.log(`Server ready at ${url}`);
```

## Core Patterns

### 1. Schema Definition

```javascript
// schema.js
import { gql } from 'graphql-tag';

export const typeDefs = gql`
  type User {
    id: ID!
    email: String!
    name: String!
    posts: [Post!]!
    createdAt: String!
  }

  type Post {
    id: