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Showing of 57What are the main benefits of using GraphQL?
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- No over-fetching: Clients get exactly what they request
- No under-fetching: Get related data in a single request
- Strong typing: Schema defines exact API contract
- Introspection: Self-documenting APIs
- Version-free: Evolve API without versioning
- Developer experience: Better tooling and debugging
- Frontend independence: Different clients can request different data
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What are the three main operation types in GraphQL?
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- Query: Read operations to fetch data
- Mutation: Write operations to modify data
- Subscription: Real-time operations for live data updates
# Query
query GetUser {
user(id: "123") { name }
}
# Mutation
mutation CreateUser {
createUser(input: { name: "John" }) {
id
name
}
}
# Subscription
subscription UserUpdates {
userUpdated(id: "123") {
name
status
}
}
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What is a GraphQL schema?
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A GraphQL schema is a contract that defines the structure of the API, including all available operations, types, and relationships. It serves as the single source of truth for what data can be fetched and how.
type User {
id: ID!
name: String!
email: String!
posts: [Post!]!
}
type Query {
user(id: ID!): User
users: [User!]!
}
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What are GraphQL scalars?
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Scalars are primitive data types that represent leaf values in GraphQL. Built-in scalars include:
String: UTF-8 character sequenceInt: 32-bit signed integerFloat: Double-precision floating-pointBoolean: true or falseID: Unique identifier
You can also define custom scalars:
scalar Date
scalar Email
scalar URL
type User {
id: ID!
email: Email!
birthDate: Date
}
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Explain the difference between nullable and non-nullable fields in GraphQL
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In GraphQL, fields are nullable by default. The exclamation mark (!) makes a field non-nullable.
type User {
id: ID! # Required field
name: String! # Required field
email: String # Optional field (can be null)
age: Int # Optional field
posts: [Post!]! # Required array of required Posts
tags: [String] # Optional array of optional strings
}
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What are GraphQL object types and how do you define them?
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Object types represent entities in your domain with named fields. They're the most common type in GraphQL schemas.
type User {
id: ID!
name: String!
email: String!
posts: [Post!]!
createdAt: String!
}
type Post {
id: ID!
title: String!
content: String!
author: User!
published: Boolean!
}
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What are GraphQL enums and when would you use them?
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Enums define a set of possible values for a field, providing type safety and validation.
enum UserRole {
ADMIN
MODERATOR
USER
GUEST
}
enum PostStatus {
DRAFT
PUBLISHED
ARCHIVED
}
type User {
id: ID!
name: String!
role: UserRole!
}
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What are input types and how do they differ from regular types?
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Input types are used for arguments in mutations and queries. They can only contain scalars, enums, lists, and other input types.
input CreateUserInput {
name: String!
email: String!
age: Int
}
input UpdateUserInput {
name: String
email: String
age: Int
}
type Mutation {
createUser(input: CreateUserInput!): User!
updateUser(id: ID!, input: UpdateUserInput!): User!
}
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What are arguments in GraphQL queries?
What are aliases in GraphQL?
What are variables in GraphQL?
How do mutations differ from queries?
What are resolvers in GraphQL?
What are the four resolver arguments?
What is Apollo Server?
What is Apollo Client?
What is GraphQL Playground?
What are interfaces in GraphQL?
What are union types in GraphQL?
What are fragments in GraphQL?
What are inline fragments?
What are directives in GraphQL?
What is the best practice for mutation input design?
How do you handle errors in mutations?
What are GraphQL subscriptions?
How are subscriptions typically implemented?
What is the resolver chain?
How do you handle asynchronous operations in resolvers?
What is the N+1 query problem in GraphQL?
How do you solve the N+1 problem with DataLoader?
What are some GraphQL caching strategies?
How do you implement authentication in GraphQL?
How do you implement authorization in GraphQL?
How do you prevent introspection attacks?
What is schema-first vs code-first development?
What are some popular GraphQL code generators?
How do you handle file uploads in GraphQL?
What is the DataLoader pattern?
What are GraphQL middlewares and how do you use them?
How do you version a GraphQL API?
What is the difference between GraphQL and gRPC?
What are some GraphQL testing strategies?
How do you implement cursor-based pagination?
How do you handle GraphQL error handling and logging?
What are the limitations of GraphQL?
What is query complexity analysis?
How do you implement query timeout and rate limiting?
What are some common GraphQL security vulnerabilities?
What is GraphQL Federation?
What is schema stitching?
How do you implement real-time features with subscriptions?
What is query whitelisting/persisted queries?
How do you implement custom directives?
How do you handle database transactions in GraphQL?
What is Apollo Federation vs Schema Stitching?
How do you migrate from REST to GraphQL?
What is the GraphQL execution algorithm?
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