Apollo Federation concepts in GraphQL - Mini Project: Build & Apply

Building a Simple Apollo Federation Setup

📖 Scenario: You are working on a project where multiple teams manage different parts of a product catalog. Each team has its own GraphQL service. You want to combine these services into one unified graph so clients can query all product information easily.

🎯 Goal: Build a basic Apollo Federation setup with two services: products and reviews. Each service defines its own GraphQL schema. Then create a gateway schema that composes these services into one federated graph.

📋 What You'll Learn

Create a products service schema with a Product type having id and name fields

Create a reviews service schema with a Review type and extend the Product type to add reviews field

Use Apollo Federation directives like @key and @extends correctly

Create a gateway schema that composes the two services into one federated graph

💡 Why This Matters

🌍 Real World

Large companies often split their GraphQL APIs into multiple services owned by different teams. Apollo Federation helps combine these into one seamless API for clients.

💼 Career

Understanding Apollo Federation is valuable for backend developers working with GraphQL in microservice architectures.

1

Create the Products Service Schema

Create a GraphQL schema string called productsTypeDefs that defines a Product type with fields id (ID!) and name (String!). Add the Apollo Federation directive @key(fields: "id") to the Product type.

GraphQL

# Your code here to create productsTypeDefs schema string

Need a hint?

Use backticks to create a multi-line string. The @key directive marks the primary key field for federation.

2

Create the Reviews Service Schema

Create a GraphQL schema string called reviewsTypeDefs that defines a Review type with fields id (ID!) and content (String!). Extend the Product type with @extends and @key(fields: "id") directives, adding a reviews field that returns a list of Review.

GraphQL

const productsTypeDefs = `
  type Product @key(fields: "id") {
    id: ID!
    name: String!
  }
`;

# Your code here to create reviewsTypeDefs schema string

Need a hint?

Use extend type to add fields to Product in the reviews service. Mark id as @external because it is owned by the products service.

3

Create the Apollo Gateway Setup

Create a variable called gateway that initializes an ApolloGateway instance with a serviceList containing two services: one named products with URL http://localhost:4001/graphql and one named reviews with URL http://localhost:4002/graphql.

GraphQL

const productsTypeDefs = `
  type Product @key(fields: "id") {
    id: ID!
    name: String!
  }
`;

const reviewsTypeDefs = `
  type Review {
    id: ID!
    content: String!
  }

  extend type Product @key(fields: "id") {
    id: ID! @external
    reviews: [Review]
  }
`;

# Your code here to create ApolloGateway instance called gateway

Need a hint?

Use new ApolloGateway({ serviceList: [...] }) to configure the gateway with the two services.

4

Complete the Apollo Server Setup with Gateway

Create a variable called server that initializes an ApolloServer instance using the gateway variable. Set subscriptions to false in the server options.

GraphQL

const productsTypeDefs = `
  type Product @key(fields: "id") {
    id: ID!
    name: String!
  }
`;

const reviewsTypeDefs = `
  type Review {
    id: ID!
    content: String!
  }

  extend type Product @key(fields: "id") {
    id: ID! @external
    reviews: [Review]
  }
`;

const gateway = new ApolloGateway({
  serviceList: [
    { name: 'products', url: 'http://localhost:4001/graphql' },
    { name: 'reviews', url: 'http://localhost:4002/graphql' }
  ]
});

# Your code here to create ApolloServer instance called server with gateway and subscriptions false

Need a hint?

Pass the gateway variable to the ApolloServer constructor and disable subscriptions.