Why federation scales GraphQL - See It in Action

Building a Scalable GraphQL API with Federation

📖 Scenario: You are working on a growing e-commerce platform. As the platform expands, different teams manage different parts of the data: products, users, and orders. To keep the API fast and scalable, you want to use GraphQL federation to combine these separate services into one unified API.

🎯 Goal: Build a simple federated GraphQL setup with three services: products, users, and orders. Each service defines its own schema and shares key fields to enable federation. Then, create a gateway schema that combines them into one API.

📋 What You'll Learn

Create a GraphQL schema for the products service with a Product type and a products query.

Create a GraphQL schema for the users service with a User type and a users query.

Create a GraphQL schema for the orders service with an Order type and an orders query.

Add federation directives to share keys between services.

Create a gateway schema that composes the three services into one federated API.

💡 Why This Matters

🌍 Real World

Large companies use GraphQL federation to split their API into smaller, manageable services owned by different teams. This helps scale development and maintain performance.

💼 Career

Understanding GraphQL federation is valuable for backend developers and API architects working on scalable, modular APIs in modern web applications.

1

Create the Products Service Schema

Create a GraphQL schema for the products service. Define a Product type with fields id (ID!), name (String!), and price (Float!). Add a query products that returns a list of Product. Use the federation directive @key(fields: "id") on the Product type.

GraphQL

# Define the Product type and products query with federation key
# Your code here

Need a hint?

Use @key(fields: "id") on the Product type to enable federation. Define the products query to return a list of products.

2

Create the Users Service Schema

Create a GraphQL schema for the users service. Define a User type with fields id (ID!), username (String!), and email (String!). Add a query users that returns a list of User. Use the federation directive @key(fields: "id") on the User type.

GraphQL

type Product @key(fields: "id") {
  id: ID!
  name: String!
  price: Float!
}

extend type Query {
  products: [Product]
}

# Define the User type and users query with federation key
# Your code here

Need a hint?

Use @key(fields: "id") on the User type to enable federation. Define the users query to return a list of users.

3

Create the Orders Service Schema

Create a GraphQL schema for the orders service. Define an Order type with fields id (ID!), productId (ID!), userId (ID!), and quantity (Int!). Add a query orders that returns a list of Order. Use the federation directive @key(fields: "id") on the Order type.

GraphQL

type Product @key(fields: "id") {
  id: ID!
  name: String!
  price: Float!
}

extend type Query {
  products: [Product]
}

type User @key(fields: "id") {
  id: ID!
  username: String!
  email: String!
}

extend type Query {
  users: [User]
}

# Define the Order type and orders query with federation key
# Your code here

Need a hint?

Use @key(fields: "id") on the Order type to enable federation. Define the orders query to return a list of orders.

4

Create the Gateway Schema to Compose Services

Create a gateway schema that composes the products, users, and orders services into one federated API. Use the Apollo Federation @apollo/gateway or similar tool to combine the schemas. The gateway should be able to resolve queries across services seamlessly.

GraphQL

type Product @key(fields: "id") {
  id: ID!
  name: String!
  price: Float!
}

extend type Query {
  products: [Product]
}

type User @key(fields: "id") {
  id: ID!
  username: String!
  email: String!
}

extend type Query {
  users: [User]
}

type Order @key(fields: "id") {
  id: ID!
  productId: ID!
  userId: ID!
  quantity: Int!
}

extend type Query {
  orders: [Order]
}

# Compose the three services into a federated gateway schema
# Your code here

Need a hint?

Use Apollo Gateway's serviceList to list the three services by name and URL. This composes the federated schema.