Type definitions in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this GraphQL query?

Given this GraphQL schema:

type Book {
  title: String!
  author: String!
  pages: Int
}

type Query {
  book: Book
}

And this query:

{
  book {
    title
    pages
  }
}

Assuming the resolver returns { title: "1984", author: "Orwell", pages: 328 }, what is the query result?

A {"data":{"book":{"title":"1984","pages":328}}}

B {"data":{"book":{"title":"1984","author":"Orwell"}}}

C {"data":{"book":{"title":"1984"}}}

D {"data":{"book":{"pages":328}}}

💡 Hint

Only requested fields appear in the result.

The query asks for title and pages only, so the response includes those fields with their values.

🧠 Conceptual

intermediate

Which GraphQL type definition correctly defines a nullable field?

In GraphQL, how do you define a field that can be null?

A type User { name: String!! }

B type User { name: String }

C type User { name: String! }

D type User { name: !String }

💡 Hint

Nullable fields do not have an exclamation mark.

In GraphQL, String means the field can be null. Adding ! means it is non-nullable.

📝 Syntax

advanced

Identify the syntax error in this GraphQL type definition

Which option contains a syntax error in the GraphQL type definition?

type Product {
  id: ID!
  name: String!
  price: Float
  tags: [String!]
}

A type Product { id: ID! name String! price: Float tags: [String!] }

B type Product { id: ID! name: String! price: Float tags: [String!]! }

C } !]!gnirtS[ :sgat taolF :ecirp !gnirtS :eman !DI :di { tcudorP epyt

D ype Product { id: ID! name: String! price: Float tags: [String!]! }

💡 Hint

Check for missing colons, commas, or invalid brackets.

Option A has a syntax error: it is missing the colon (:) after the field name 'name'.

🔧 Debug

advanced

Why does this GraphQL schema cause an error?

Consider this schema snippet:

type Query {
  user(id: ID!): User
}

type User {
  id: ID!
  name: String!
  friend: User
}

Why might this schema cause an error in some GraphQL servers?

A Because 'Query' type cannot have arguments.

B Because 'User' type is missing a required field.

C Because 'id' field should not be non-nullable.

D Because the 'friend' field creates a circular reference without a resolver.

💡 Hint

Think about recursive types and resolvers.

The 'friend' field references the same 'User' type, creating a circular reference. Without proper resolver handling, some servers error out.

❓ optimization

expert

How to optimize GraphQL type definitions for large lists?

You have a GraphQL type with a field returning a large list of items:

type Query {
  allPosts: [Post!]!
}

What is the best way to optimize this type definition for performance and usability?

A Keep the list as is but add a non-null assertion to the list items.

B Change the field to return a single Post instead of a list.

C Change the field to use pagination arguments and return a paginated type instead of a large list.

D Remove the non-null assertion from the list and items to allow nulls.

💡 Hint

Think about how to handle large data sets efficiently.

Returning large lists can cause performance issues. Using pagination with arguments like limit and offset improves performance and usability.