Auth & Field Level Security
Implement a custom @auth(role:) schema directive
Field-Level Authorization: Gate Sensitive User Fields on Context Permissions
Mask the creditCardNumber field on a Payment type (show only last four)
Schema Design & Types
Library API: Book → Author resolvers
Implement a Product Catalog Filter with a Nested FilterInput
OrderStatus Enum: Resolve, Filter, and Validate Status Updates
Shopping List GraphQL Server: CRUD + Check-Off Mutation
Server-Driven UI: Component Interface Resolvers
Multi-Tenant Blogging Platform: Organization-Scoped Resolvers
Schema Design Performance & Tooling
Batch Author lookups with DataLoader to kill the N+1 in Book.author
Implement a SearchResult union with __resolveType
DataLoader batch function: return results in exact input-key order
Map Postgres unique/foreign-key violations to GraphQL error codes via resolver middleware
Mutation Returning a User | UserError Union
Node interface with a __resolveType discriminator
Custom GraphQLError Subclasses with extensions (code + HTTP status)
Implement the Bookstore GraphQL Resolvers (Query, Mutation, computed & nested fields)
Resolver Timing Wrapper: Log Slow Field Resolutions (>200ms) with Their Variables
Tenant-Aware DataLoader Caching for Multi-Tenant Data Isolation
Custom Scalars & Directives
Implement a custom `DateTime` GraphQL scalar (serialize / parseValue / parseLiteral)
Implement a custom ISO-8601 DateTime scalar
Custom Email Scalar: serialize, parseValue & parseLiteral
Enforce mutually-exclusive contact fields with the @oneOf input directive
Custom PhoneNumber Scalar with E.164 Validation
Input Validation & Query Limits
Validate mutation inputs before they reach the resolver
Query Complexity Validation Rule with @cost Directives
Query Depth Limit Validation Rule (max 5 levels)
Query Complexity Limiting Validation Rule (DoS protection)
Resolvers & Data Fetching
Batch ID Lookups with a Single Bulk WHERE-IN Query (DataLoader)
Resolve a totalSpent field that sums a user's purchases within a time range
Pagination & Search
Offset/Limit Pagination with totalCount for a Posts Query
Multi-Field Product Search with Pagination
Relay Cursor Connections: Paginated Messages Query
Mutations & Data Writes
CreatePost Mutation with Generated ID
Follow Mutation: update a join table and return the User with a recalculated followerCount
Task scheduler: toggleTask mutation that locks tasks until dependencies finish
Atomic createPost Mutation Linking Multiple Existing Tags