Depth limiting in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the result of this GraphQL query with depth limit 2?

Given a GraphQL schema with nested types, and a depth limit of 2, what will be the result of this query?

{ user { id name posts { title comments { text } } } }

Assume the depth limit blocks fields nested deeper than 2.

A {"data":{"user":{"id":"1","name":"Alice","posts":[{"title":"Post 1","comments":[{"text":"Nice!"}]}]}}}

B {"data":{"user":{"id":"1","name":"Alice"}}}

C {"errors":[{"message":"Depth limit exceeded"}]}

D {"data":{"user":{"id":"1","name":"Alice","posts":[{"title":"Post 1"},{"title":"Post 2"}]}}}

💡 Hint

Depth limit 2 means fields nested more than 2 levels are blocked.

The query requests user (level 1), posts (level 2), and comments (level 3). Since depth limit is 2, comments are blocked, so only posts' titles are returned.

🧠 Conceptual

intermediate

Why is depth limiting important in GraphQL APIs?

Choose the best reason why depth limiting is used in GraphQL APIs.

A To prevent clients from requesting too much nested data causing performance issues

B To automatically cache all nested queries for faster responses

C To allow clients to request unlimited nested data without restrictions

D To encrypt nested fields for security

💡 Hint

Think about server load and query complexity.

Depth limiting prevents clients from making very deep nested queries that can overload the server or cause slow responses.

📝 Syntax

advanced

Which GraphQL query will cause a depth limit error with max depth 3?

Given a max depth of 3, which query will exceed the depth limit?

A { user { id posts { title comments { text } } } }

B { user { id posts { title comments { text author { name } } } } }

C { user { id posts { title } } }

D { user { id name } }

💡 Hint

Count the nesting levels carefully.

Option B has nesting: user (1), posts (2), comments (3), author (4) which exceeds max depth 3.

❓ optimization

advanced

How to optimize GraphQL server to handle deep queries safely?

Which approach best optimizes a GraphQL server to safely handle deep nested queries?

A Disable introspection to prevent deep queries

B Allow all queries and rely on client to limit nesting

C Implement depth limiting middleware to reject queries exceeding max depth

D Cache all query results regardless of depth

💡 Hint

Think about server-side protections.

Depth limiting middleware protects the server by rejecting overly deep queries before execution.

🔧 Debug

expert

Why does this GraphQL query pass depth limit but still cause performance issues?

Given a depth limit of 3, this query passes but the server is slow:

{ user { posts { comments { text } } } }

Why might this happen?

A The query returns too many items at each level causing large data volume

B The depth limit is set too low to block the query

C The query syntax is invalid causing retries

D The server has no indexes on user fields

💡 Hint

Depth limit controls nesting, not number of items returned.

Even with limited depth, if each nested list is large, the total data volume can be huge causing slow performance.