Hierarchical resource paths in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested resource path matching

Consider a REST API with the following hierarchical resource paths:

/users/{userId}/posts/{postId}

If a client sends a GET request to /users/42/posts/7, what is the expected resource path matched and the extracted parameters?

A Resource path: /posts/{postId}, Parameters: postId=7

B Resource path: /users/{userId}/posts/{postId}, Parameters: userId=42, postId=7

C Resource path: /users/{userId}, Parameters: userId=42

D Resource path: /users/posts, Parameters: none

💡 Hint

Think about how hierarchical paths capture parameters at each level.

The full path /users/42/posts/7 matches the nested resource /users/{userId}/posts/{postId}. Both userId and postId are extracted from the URL.

🧠 Conceptual

intermediate

Understanding hierarchical resource path design

Why is it beneficial to design REST API resource paths hierarchically, such as /users/{userId}/posts/{postId}, instead of flat paths like /posts/{postId} only?

A It prevents clients from accessing nested resources.

B It reduces the number of API endpoints needed by combining unrelated resources.

C It makes the API slower because of longer URLs.

D It helps organize resources logically and clarifies ownership or relationships between resources.

💡 Hint

Think about how URLs reflect real-world relationships.

Hierarchical paths show how resources relate, like posts belonging to a user. This makes APIs easier to understand and use.

🔧 Debug

advanced

Identify the error in hierarchical path matching

Given the following API route definitions:

/users/{userId}/posts/{postId}
/users/{userId}/posts
/users/all

A GET request to /users/all/posts returns a 404 error. Why?

A Because <code>/users/all/posts</code> matches <code>/users/{userId}/posts</code>; 'all' is treated as a userId but no posts exist for it.

B Because <code>/users/all</code> is a static path and cannot be followed by /posts.

C Because the API does not support nested resources under static paths.

D Because the route <code>/users/{userId}/posts</code> requires a numeric userId.

💡 Hint

Consider how path parameters and static segments are matched.

The path /users/all/posts tries to match /users/{userId}/posts with userId='all'. Since 'all' is not a user with posts, it returns 404. The static path /users/all does not have a nested /posts route.

📝 Syntax

advanced

Correct hierarchical path syntax

Which of the following is the correct syntax for defining a hierarchical resource path with two parameters in a REST API?

A /users/userId/posts/postId

B /users/:userId/posts/:postId/

C /users/{userId}/posts/{postId}

D /users/{userId}/posts/postId

💡 Hint

Look for the standard placeholder format for path parameters.

The standard syntax uses curly braces {} to denote parameters in REST API paths, e.g., {userId}.

🚀 Application

expert

Determine the number of unique resource paths

An API defines these hierarchical resource paths:

/companies/{companyId}/departments/{departmentId}/employees/{employeeId}
/companies/{companyId}/departments/{departmentId}
/companies/{companyId}

If the API has 3 companies, each with 4 departments, and each department has 10 employees, how many unique resource paths exist for /companies/{companyId}/departments/{departmentId}/employees/{employeeId}?

A 120

B 17

C 70

D 30

💡 Hint

Multiply the counts at each level of the hierarchy.

There are 3 companies × 4 departments each × 10 employees each = 120 unique employee resource paths.