graphql-apollo-server

# Apollo Server Skill

> Deploy production-ready GraphQL APIs

## Overview

Learn to build scalable GraphQL servers with Apollo Server 4, including middleware integration, custom plugins, federation, and production best practices.

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## Quick Reference

| Feature | Package | Purpose |
|---------|---------|---------|
| Server | `@apollo/server` | Core server |
| Express | `@apollo/server/express4` | Express integration |
| Plugins | `@apollo/server/plugin/*` | Extensibility |
| Federation | `@apollo/subgraph` | Microservices |

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## Core Setup

### 1. Basic Server (Express)

```typescript
import { ApolloServer } from '@apollo/server';
import { expressMiddleware } from '@apollo/server/express4';
import { ApolloServerPluginDrainHttpServer } from '@apollo/server/plugin/drainHttpServer';
import express from 'express';
import http from 'http';
import cors from 'cors';

interface Context {
  user: User | null;
  dataSources: DataSources;
}

async function startServer() {
  const app = express();
  const httpServer = http.createServer(app);

  const server = new ApolloServer<Context>({
    typeDefs,
    resolvers,
    plugins: [
      // Graceful shutdown
      ApolloServerPluginDrainHttpServer({ httpServer }),
    ],
  });

  await server.start();

  app.use(
    '/graphql',
    cors({ origin: ['http://localhost:3000'], credentials: true }),
    express.json(),
    expressMiddleware(server, {
      context: async ({ req }) => ({
        user: await getUser(req),
        dataSources: createDataSources(),
      }),
    }),
  );

  httpServer.listen(4000, () => {
    console.log('Server ready at http://localhost:4000/graphql');
  });
}
```

### 2. Production Configuration

```typescript
const server = new ApolloServer<Context>({
  typeDefs,
  resolvers,

  // Error formatting
  formatError: (error) => {
    console.error('GraphQL Error:', error);

    // Hide internal errors in production
    if (process.env.NODE_ENV === 'production') {
      if (error.extensions?.code