Learn GraphQL federation

src/pages/learn/_meta.ts

@@ -22,4 +22,5 @@ export default {
   "global-object-identification": "",
   caching: "",
   security: "",
+  federation: "",
 }

src/pages/learn/federation.mdx

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+---
+sidebarTitle: Federation
+---
+
+import { Tabs } from 'nextra/components'
+
+# GraphQL Federation
+
+As applications grow more complex, traditional monolithic approaches often fall short. At scale,
+monolithic architectures can become cumbersome, brittle, and increasingly hard to test and validate.
+This has led to a rise in the adoption of new patterns like distributed systems and microservices.
+In some ways, GraphQL Federation is like microservices for GraphQL – an architectural pattern that
+has found particular resonance in the GraphQL ecosystem.
+
+GraphQL Federation gained widespread adoption after
+[Apollo GraphQL introduced Apollo Federation in 2019](https://www.apollographql.com/blog/apollo-federation-f260cf525d21).
+Their implementation has become a reference point for the GraphQL community, helping establish
+federation as a standard architectural pattern for building a distributed graph in the GraphQL
+ecosystem.
+
+With more companies and developers seeing the benefits of building a distributed graph with
+federation, the GraphQL ecosystem is now moving towards standardization of federation patterns. The
+GraphQL Foundation's
+[Composite Schema Working Group](https://github.com/graphql/composite-schemas-wg), which includes
+engineers from various organizations across the industry including
+[Apollo GraphQL](https://apollographql.com), [ChilliCream](https://chillicream.com/),
+[Graphile](https://www.graphile.org/), [Hasura](https://hasura.io/),
+[Netflix](https://www.netflix.com/) and [The Guild](https://the-guild.dev), is actively working on
+creating
+[an official specification for GraphQL Federation](https://github.com/graphql/composite-schemas-spec).
+This effort aims to standardize how GraphQL services can be composed and executed across distributed
+systems, while ensuring room for innovation and different implementations.
+
+## What is federation?
+
+Architecturally, federation is an approach to organizing and managing distributed systems. At its
+core, federation allows autonomous components to work together while maintaining their independence.
+Think of it like a federal government system: individual states maintain their sovereignty while
+cooperating under a central authority for shared concerns.
+
+In software architecture, federation enables organizations to:
+
+- Distribute responsibility across independent teams
+- Scale different components independently
+- Maintain clear boundaries between different domains
+- Enable autonomous development and deployment
+- Reduce single points of failure
+
+Think of the "Login with Google" or "Login with Facebook" buttons you see on websites. This is
+federation in action: you can use your Google or Facebook account to log into many different
+websites, even though each company manages their own login system separately.
+
+## What Is Federated GraphQL?
+
+GraphQL Federation applies those principles to GraphQL APIs. It enables organizations to build a
+unified GraphQL schema from multiple independent services (most often called subgraphs), each
+responsible for its portion of the application's data graph.
+
+Consider an e-commerce platform: You might have separate teams managing products, user accounts, and
+order processing. With GraphQL Federation, each team can:
+
+- Define their own GraphQL schema
+- Deploy and scale their service independently
+- Contribute to a unified GraphQL API without tight coupling
+- Maintain ownership of their domain-specific logic
+
+The magic happens through a federated gateway that acts as the central coordinator, composing these
+separate schemas into a unified schema that clients can query.
+
+## How Federation Works in GraphQL
+
+The federation process involves several key components:
+
+- **Subgraphs**: Individual services that define their own GraphQL schemas and resolvers
+- **Gateway**: A specialized service that sits between clients and your federated services
+- **Schema composition**: The process of merging schemas while resolving references between them,
+  often handled by schema registries.
+
+<Tabs items={['Products subgraph', 'Orders subgraph', 'Users subgraph']}> <Tabs.Tab>
+
+```graphql
+type Product @key(fields: "id") {
+  id: ID!
+  title: String!
+  price: Float!
+  inStock: Boolean!
+}
+```
+
+</Tabs.Tab> <Tabs.Tab>
+
+```graphql
+type Order @key(fields: "id") {
+  id: ID!
+  products: [Product!]!
+  total: Float!
+}
+
+type Product {
+  id: ID!
+}
+```
+
+</Tabs.Tab> <Tabs.Tab>
+
+```graphql
+type Query {
+  user(id: ID!): User
+}
+
+type User {
+  id: ID!
+  name: String!
+  email: String
+  orders: [Order!]!
+}
+
+type Order {
+  id: ID!
+}
+```
+
+</Tabs.Tab> </Tabs>
+
+### Schema Composition
+
+Let's break down schema composition in GraphQL federation with more detail and examples. Schema
+composition is the process where multiple subgraph schemas are combined into one unified schema.
+It's more complex than simply merging schemas together, though, because it needs to handle
+relationships, detect incompatibilities, and ensure types are properly connected across services and
+subgraphs.
+
+Based on the examples we provided before, here's the unified schema GraphQL clients will see and can
+query:
+
+```graphql
+type Query {
+  user(id: ID!): User
+}
+
+type User {
+  id: ID!
+  name: String!
+  email: String
+  orders: [Order!]!
+}
+
+type Order {
+  id: ID!
+  products: [Product!]!
+  total: Float!
+}
+
+type Product {
+  id: ID!
+  title: String!
+  price: Float!
+  inStock: Boolean!
+}
+```
+
+This unified schema combines types and fields from all three subgraphs (Users, Orders, and
+Products), allowing clients to seamlessly query across these domains.
+
+### Gateway
+
+The federation gateway is the entry point to your distributed data graph. It presents a unified
+GraphQL endpoint to clients and handles the complexity of routing queries to the appropriate
+subgraphs and assembling the results, and often provides caching and performance optimizations.
+
+```mermaid
+graph TD
+  Client --> FederationGateway
+  FederationGateway --> UsersService
+  FederationGateway --> OrdersService
+  FederationGateway --> ProductsService
+
+  Client[Client]
+  FederationGateway[Gateway]
+  UsersService[Users Service]
+  OrdersService[Orders Service]
+  ProductsService[Products Service]
+```
+
+Take the following query as an example:
+
+```graphql
+query {
+  user(id: "123") {
+    # Resolved by Users subgraph
+    name
+    orders {
+      # Resolved by Orders subgraph
+      id
+      products {
+        # Resolved by Products subgraph
+        title
+        price
+      }
+    }
+  }
+}
+```
+
+The gateway will route parts of the query to the appropriate subgraphs, collect the results, and
+assemble them into a single response that the client can consume.
+
+## Benefits of GraphQL Federation
+
+### Domain-Driven Development
+
+Teams can work independently on their services while contributing to a cohesive API. This autonomy
+accelerates development and reduces coordination overhead.
+
+### Service Integrity Protection
+
+The schema composition step verifies integration between services by ensuring that changes in
+individual subgraphs do not conflict with other subgraphs.
+
+### Scalability and Performance
+
+Subgraphs and services can be scaled independently based on their specific requirements. The product
+catalog might need different scaling characteristics than the order processing system.
+
+### Single, Unified API
+
+Thanks to GraphQL, clients get a single endpoint with unified schema spanning multiple subgraphs.
+The complexity of distributed systems is hidden. The gateway ensures every query reaches its
+destination and returns with the right data.
+
+## Is GraphQL Federation Right for You?
+
+GraphQL Federation aligns naturally with Domain Driven Design (DDD) principles by allowing teams to
+maintain clear boundaries around their domains, while maintaining explicit integration points
+through the GraphQL schema. It is particularly valuable for organizations where multiple teams need
+to work independently on different parts of the GraphQL API, with the flexibility to use different
+technologies and programming languages.
+
+However, implementing Federation requires substantial infrastructure support, including a dedicated
+team to manage the gateway, schema registry, to help connect subgraphs to the federated API and guide
+teams on best practices.
+
+Before adopting Federation, it's crucial to consider whether your organization truly needs this
+level of complexity.
+
+Meta (formerly Facebook), [where GraphQL was created](/blog/2015-09-14-graphql/), has continued to
+use a monolithic GraphQL API since 2012. However, companies like
+[Netflix](https://netflixtechblog.com/how-netflix-scales-its-api-with-graphql-federation-part-1-ae3557c187e2),
+[Expedia Group](https://youtu.be/kpeVT7J6Bsw?si=srGWsoxf3kTmneTu&t=79),
+[Volvo](https://www.apollographql.com/blog/volvo-cars-drives-into-the-future-of-online-car-shopping-with-the-supergraph),
+and [Booking](https://youtu.be/2KsP_x50tGk?si=mu-MOG-xZQSDNDjh&t=478) have adopted Federation to
+better align with their organizational structures and microservices architecture.
+
+As you see, many industry leaders successfully federated their GraphQL APIs, proving that it works
+reliably for large-scale production applications.
+
+## Getting Started with GraphQL Federation
+
+If you're considering adopting GraphQL Federation, here are some steps to get started:
+
+1. **Identify Service Boundaries**: Define clear boundaries between different domains in your
+   application
+2. [**Design Schemas**](/learn/schema/ 'Learn about the different elements of the GraphQL type system'):
+   Create schemas that reflect these boundaries while considering how they'll interact
+3. [**Implement Subgraphs**](/community/tools-and-libraries/?tags=server 'Discover a list of GraphQL servers in our Tools and Libraries page'):
+   Build individual services that implement their portion of the schema
+4. [**Set Up a Gateway**](/community/tools-and-libraries/?tags=gateways-supergraphs 'Discover a list of GraphQL gateways in our Tools and Libraries page'):
+   Deploy a federation gateway to compose and serve the unified schema
+5. [**Use a Schema Registry**](/community/tools-and-libraries/?tags=schema-registry 'Discover a list of GraphQL schema registries in our Tools and Libraries page'):
+   Manage schema composition and validation to ensure integrity across subgraphs
+
+When migrating from a monolithic GraphQL API to Federation, the simplest starting point is to treat
+your existing schema as your first subgraph. From there, you can follow the steps above to gradually
+decompose your schema into smaller pieces.