Learn GraphQL federation

src/pages/learn/_meta.ts

@@ -20,4 +20,5 @@ export default {
   pagination: "",
   "global-object-identification": "",
   caching: "",
+  federation: "",
 }

src/pages/learn/federation.mdx

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+---
+sidebarTitle: Federation
+---
+
+import { Tabs } from 'nextra/components'
+
+# GraphQL Federation
+
+In today's world of distributed systems and microservices,
+organizations face the challenge of efficiently managing and scaling their APIs.
+As applications grow more complex, traditional monolithic approaches often fall short.
+This is where federation comes into play - 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 in the GraphQL ecosystem.
+
+The GraphQL ecosystem is 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, ChilliCream, Graphile, Hasura, Netflix and The Guild,
+is actively working on creating an official specification for GraphQL Federation.
+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?
+
+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 API without tight coupling
+- Maintain ownership of their domain-specific logic
+
+The magic happens through a federated gateway that acts as the central coordinator, combining 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, because it needs to handle relationships, detect incompatibilities, and ensure types are properly connected across services.
+
+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,
+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 in the federation.
+
+### Scalability and Performance
+
+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 gateway, clients get a single endpoint with unified schema.
+The complexity of distributed systems is hidden.
+The gateway ensures every query reaches its destination and returns with the right data.
+
+## Federation vs. Monolithic Architecture
+
+While monolithic GraphQL APIs have their place, federation offers several advantages for larger applications:
+
+| **Aspect**        | **Monolithic GraphQL**            | **Federated GraphQL**         |
+| ----------------- | --------------------------------- | ----------------------------- |
+| Development Speed | Initially faster                  | Better for long-term velocity |
+| Team Coordination | Requires significant coordination | Enables independence          |
+| Deployment        | All-or-nothing                    | Independent deployments       |
+| Scaling           | Entire system scales together     | Independent scaling           |
+
+## Real-World Implementations
+
+GraphQL Federation is adopted by tech giants such as
+[Netlifx](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).
+
+Many industry leaders successfully use GraphQL federation at scale, proving that federation works reliably for large-scale production applications.
+
+## Getting Started with GraphQL Federation
+
+To implement GraphQL federation, organizations should:
+
+1. **Identify Service Boundaries**: Define clear boundaries between different domains in your application
+2. **Design Schemas**: Create schemas that reflect these boundaries while considering how they'll interact
+3. **Implement Subgraphs**: Build individual services that implement their portion of the schema
+4. **Set Up Gateway**: Deploy a federation gateway to compose and serve the unified schema
+5. **Monitor and Optimize**: Implement monitoring and continuously optimize query performance
+
+Organizations can gradually migrate from a monolithic to federated GraphQL, one service at a time.