GraphQL Schema and API Design Guide
Design a well-structured, performant GraphQL schema with best practices for queries, mutations, subscriptions, and error handling.
Prompt Template
You are a senior API architect specializing in GraphQL. Help me design a production-ready GraphQL schema for the following application. **Application:** [e.g., multi-tenant project management SaaS] **Key entities:** [e.g., Users, Projects, Tasks, Comments, Teams] **Auth model:** [e.g., JWT with role-based access — admin, member, viewer] **Real-time needs:** [e.g., task status updates, new comments] **Existing data sources:** [e.g., PostgreSQL, Redis cache, external REST APIs] Deliver: 1. **Schema Design** — complete SDL with types, inputs, enums, interfaces, and unions where appropriate 2. **Query Design** — top-level queries with pagination (cursor-based), filtering, and sorting arguments 3. **Mutation Design** — mutations with proper input types, validation rules, and error union types 4. **Subscription Design** — real-time subscriptions for the specified use cases 5. **Relay Compliance** — Node interface, connection types, and global IDs if applicable 6. **N+1 Prevention** — DataLoader patterns and resolver optimization notes 7. **Auth Directives** — custom directives or middleware patterns for field-level authorization 8. **Error Handling** — structured error types vs GraphQL errors, when to use each 9. **Versioning Strategy** — how to evolve the schema without breaking clients 10. **Performance Considerations** — query complexity limits, depth limits, persisted queries Include inline comments explaining design decisions and trade-offs.
Example Output
GraphQL Schema: Project Management SaaS
Core Types
interface Node {
id: ID!
}
type User implements Node {
id: ID!
email: String!
displayName: String!
role: UserRole!
teams: [Team!]!
createdAt: DateTime!
}
enum UserRole {
ADMIN
MEMBER
VIEWER
}
type Project implements Node {
id: ID!
name: String!
description: String
team: Team!
tasks(first: Int, after: String, filter: TaskFilter): TaskConnection!
createdAt: DateTime!
updatedAt: DateTime!
}
# Cursor-based pagination
type TaskConnection {
edges: [TaskEdge!]!
pageInfo: PageInfo!
totalCount: Int!
}
Mutations with Error Unions
union CreateProjectResult = CreateProjectSuccess | ValidationError | AuthorizationError
type CreateProjectSuccess {
project: Project!
}
mutation {
createProject(input: CreateProjectInput!): CreateProjectResult!
}
N+1 Prevention
Use DataLoader for all `team`, `user`, and `tasks` resolvers. Batch by parent ID and cache per-request.
Auth Directive
directive @auth(requires: UserRole!) on FIELD_DEFINITION
Query Complexity
Set max depth: 7, max complexity: 1000. Use `graphql-query-complexity` for cost analysis.
Tips for Best Results
- 💡Start with your domain entities and relationships before writing resolvers
- 💡Use cursor-based pagination from day one — offset pagination breaks with real-time data
- 💡Return union types from mutations instead of throwing errors for expected failure cases
- 💡Add a query complexity analyzer to prevent abusive nested queries in production
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