Apollo Federation Schema Authoring

Federation 2 Schema Setup

@link

extend schema
  @link(url: "https://specs.apollo.dev/federation/v2.12",
        import: ["@key", "@shareable", "@external", "@requires", "@provides"])

Core Directives Quick Reference

@key

type Product @key(fields: "id")

@shareable

type Position @shareable { x: Int! }

@external

weight: Int @external

@requires

shippingCost: Int @requires(fields: "weight")

@provides

@provides(fields: "name")

@override

@override(from: "Products")

@inaccessible

internalId: ID! @inaccessible

@interfaceObject

type Media @interfaceObject

Reference Files

• Directives - All federation directives with syntax, examples, and rules
• Schema Patterns - Multi-subgraph patterns and recipes
• Composition - Composition rules, error codes, and debugging

Key Patterns

Entity Definition

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

Entity Contributions Across Subgraphs

# Products subgraph
type Product @key(fields: "id") {
  id: ID!
  name: String!
  price: Int
}

# Reviews subgraph
type Product @key(fields: "id") {
  id: ID!
  reviews: [Review!]!
  averageRating: Float
}

Computed Fields with @requires

type Product @key(fields: "id") {
  id: ID!
  size: Int @external
  weight: Int @external
  shippingEstimate: String @requires(fields: "size weight")
}

Value Types with @shareable

type Money @shareable {
  amount: Int!
  currency: String!
}

Entity Stub (Reference Without Contributing)

type Product @key(fields: "id", resolvable: false) {
  id: ID!
}

Ground Rules

• ALWAYS use Federation 2.x syntax with

  @link

  directive
• ALWAYS import only the directives your subgraph uses
• NEVER use

  @shareable

  without ensuring all subgraphs return identical values for that field
• PREFER

  @key

  with single ID field for simple entity identification
• USE

  rover supergraph compose

  to validate composition locally
• USE

  rover subgraph check

  to validate against production supergraph