Schema evolution strategies in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a new optional field to a GraphQL type without breaking existing queries.

GraphQL

type User { id: ID! name: String! [1] }

Drag options to blanks, or click blank then click option'

Aage: Int!

Dage: Int

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a required field (!) breaks existing queries.

Forgetting to add the new field to the type.

Adding a new optional field (without the exclamation mark) allows existing queries to work without requiring the new field.

2fill in blank

medium

Complete the code to deprecate a field in a GraphQL schema.

GraphQL

type User { id: ID! name: String! oldField: String [1] }

Drag options to blanks, or click blank then click option'

A@deprecated(reason: "")

B@deprecated

C@deprecated(reason: "Use newField instead")

D@deprecated(reason: 123)

Attempts:

3 left

💡 Hint

Common Mistakes

Using @deprecated without a reason.

Providing a non-string reason.

The @deprecated directive with a reason string marks a field as deprecated and informs clients what to use instead.

3fill in blank

hard

Fix the error in the schema evolution by correctly renaming a field using a deprecation strategy.

GraphQL

type User { id: ID! name: String! [1]: String @deprecated(reason: "Use fullName instead") fullName: String! }

Drag options to blanks, or click blank then click option'

AoldName

BfullName

Cfullname

DnameOld

Attempts:

3 left

💡 Hint

Common Mistakes

Deprecating the new field instead of the old one.

Renaming the field without deprecation.

The old field name should be kept and marked deprecated, while the new field is added with the new name.

4fill in blank

hard

Fill both blanks to add a new enum value safely and deprecate an old one.

GraphQL

enum Status { ACTIVE [1] INACTIVE [2] }

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APENDING

BDEPRECATED

C@deprecated(reason: "Use PENDING instead")

DNEW

Attempts:

3 left

💡 Hint

Common Mistakes

Removing old enum values directly.

Not marking deprecated enum values.

Adding a new enum value 'PENDING' is safe. Deprecating 'INACTIVE' with a reason informs clients to use PENDING instead.

5fill in blank

hard

Fill all three blanks to safely evolve a GraphQL input type by adding a new optional field and deprecating an old one.

GraphQL

input UserInput { username: String! [1]: String [2] [3] }

Drag options to blanks, or click blank then click option'

Aemail

B@deprecated(reason: "Use contactEmail instead")

CcontactEmail: String

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Making new fields required.

Removing old fields without deprecation.

Adding 'email' as an optional field, marking it deprecated, and adding 'contactEmail' as the new field is a safe evolution.

Practice

1. What is the main purpose of schema evolution in GraphQL APIs?

easy

A. To update the API without breaking existing client applications

B. To remove all old fields immediately from the schema

C. To prevent any changes to the API once deployed

D. To make all fields mandatory for clients

Solution

1. Step 1: Understand schema evolution concept

   Schema evolution allows changes to the API while keeping existing clients working.

2. Step 2: Identify the correct purpose

   Removing fields immediately or making all fields mandatory breaks clients, so those are incorrect.

3. Final Answer:

   To update the API without breaking existing client applications -> Option A

4. Quick Check:

   Schema evolution = safe API updates [OK]

Hint: Schema evolution means safe API changes without breaking clients [OK]

Common Mistakes:

• Thinking schema evolution means removing fields immediately
• Believing all fields must be mandatory
• Assuming no changes are allowed after deployment

2. Which of the following is the correct way to mark a field as deprecated in a GraphQL schema?

easy

A. type User { name: String @remove(reason: "Use fullName instead") }

B. type User { name: String deprecated: true }

C. type User { name: String @deprecated(reason: "Use fullName instead") }

D. type User { name: String deprecated(reason: "Use fullName instead") }

Solution

1. Step 1: Recall GraphQL deprecation syntax

   GraphQL uses the @deprecated directive with a reason argument to mark fields deprecated.

2. Step 2: Check each option's syntax

   type User { name: String @deprecated(reason: "Use fullName instead") } uses correct @deprecated directive syntax; others are invalid or incorrect.

3. Final Answer:

   type User { name: String @deprecated(reason: "Use fullName instead") } -> Option C

4. Quick Check:

   @deprecated directive syntax = type User { name: String @deprecated(reason: "Use fullName instead") } [OK]

Hint: Use @deprecated(reason: "...") to mark fields deprecated [OK]

Common Mistakes:

• Using deprecated: true instead of @deprecated directive
• Using @remove directive which does not exist
• Omitting the @ symbol before deprecated

3. Given this GraphQL schema snippet:

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

type User {
  id: ID!
  name: String
  email: String @deprecated(reason: "Use contactEmail instead")
  contactEmail: String
}

What happens if a client queries for email field?

medium

A. The query succeeds but clients get a deprecation warning for email

B. The query fails because email is removed

C. The query returns null for email always

D. The query returns contactEmail value instead of email

Solution

1. Step 1: Understand @deprecated behavior in GraphQL

   Deprecated fields still exist and return data but signal clients to avoid using them.

2. Step 2: Analyze the query effect

   Querying email returns its value but clients should see a deprecation warning.

3. Final Answer:

   The query succeeds but clients get a deprecation warning for email -> Option A

4. Quick Check:

   Deprecated fields return data with warnings [OK]

Hint: Deprecated fields still return data but warn clients [OK]

Common Mistakes:

• Assuming deprecated fields are removed immediately
• Thinking deprecated fields return null
• Believing deprecated fields auto-redirect to new fields

4. Consider this schema update attempt:

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

# Update:
type User {
  id: ID!
  name: String
  contactEmail: String
}

What is the main problem with this update?

medium

A. GraphQL does not allow adding new fields to existing types

B. Adding contactEmail without deprecating email causes syntax error

C. You must rename email to contactEmail in one step

D. Removing email field breaks existing clients still using it

Solution

1. Step 1: Identify schema evolution best practice

   Removing fields immediately breaks clients that still query those fields.

2. Step 2: Analyze the update

   The update removes email without deprecation, causing breaking changes.

3. Final Answer:

   Removing email field breaks existing clients still using it -> Option D

4. Quick Check:

   Immediate removal breaks clients [OK]

Hint: Never remove fields immediately; deprecate first [OK]

Common Mistakes:

• Thinking adding fields causes syntax errors
• Believing renaming must be one-step without deprecation
• Assuming GraphQL forbids adding new fields

5. You want to evolve a GraphQL schema by replacing a field phone with mobilePhone without breaking clients. Which strategy is best?

hard

A. Remove phone immediately and add mobilePhone

B. Add mobilePhone as optional, deprecate phone with reason, keep both for now

C. Rename phone to mobilePhone directly without deprecation

D. Keep only phone and do not add mobilePhone

Solution

1. Step 1: Apply schema evolution best practice

   Adding new fields as optional and deprecating old ones avoids breaking clients.

2. Step 2: Evaluate options

   Add mobilePhone as optional, deprecate phone with reason, keep both for now follows best practice; others cause breaking changes or no evolution.

3. Final Answer:

   Add mobilePhone as optional, deprecate phone with reason, keep both for now -> Option B

4. Quick Check:

   Deprecate old, add new optional field [OK]

Hint: Add new optional field, deprecate old with reason [OK]

Common Mistakes:

• Removing old field immediately
• Renaming fields without deprecation
• Not adding new field at all