Why federation scales GraphQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a federated service with a key directive.

GraphQL

type Product @key(fields: "[1]") { id: ID! name: String }

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Aprice

Bsku

Cid

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-unique field like 'name' as the key.

Omitting the @key directive entirely.

The @key directive specifies the primary field used to identify the entity across services. Here, id is the correct key.

2fill in blank

medium

Complete the code to extend a type from another service in federation.

GraphQL

extend type User @key(fields: "[1]") { id: ID! username: String }

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Aid

Bprofile

Cemail

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-key field like 'username' in the @key directive.

Forgetting to use the extend keyword.

When extending a type, the @key directive must use the field that uniquely identifies the entity, typically id.

3fill in blank

hard

Fix the error in the federation SDL by completing the missing directive.

GraphQL

type Review { id: ID! body: String author: User [1] }

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A@external

B@provides

C@requires

D@key

Attempts:

3 left

💡 Hint

Common Mistakes

Using @key on a field that is not a key.

Using @provides or @requires incorrectly.

The @external directive marks fields that are owned by another service but referenced here, which is necessary for federation to work correctly.

4fill in blank

hard

Fill both blanks to complete the resolver that fetches a federated entity by its key.

GraphQL

User: { __resolveReference([1]) { return fetchUserById([1].[2]); } }

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Aid

Buser

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong argument name in the resolver.

Using a non-key field to fetch the entity.

The resolver receives the reference object as user, and the key field to fetch the user is id.

5fill in blank

hard

Fill all three blanks to complete the federated schema with multiple services.

GraphQL

schema { query: [1] } type [2] { products: [Product] } type Product @key(fields: "[3]") { id: ID! name: String }

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AQuery

BProduct

Cid

DMutation

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Mutation' instead of 'Query' as the root type.

Using 'Product' as the root query type name.

Using a non-key field in the @key directive.

The schema's query root is Query. The type containing the products field is also Query. The key field for Product is id.