REST API design for systems in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding REST API Statelessness

Which statement best describes the statelessness principle in REST API design?

A API requests can depend on previous requests to complete successfully.

B The server must store session information to track user state between requests.

C Each API request must contain all information needed to process it, without relying on stored context on the server.

D Clients should maintain no state and rely on the server to remember previous interactions.

💡 Hint

Think about how REST APIs handle client-server communication without storing session data.

REST APIs are stateless, meaning each request is independent and contains all necessary information. The server does not store client context between requests.

❓ Architecture

intermediate

Choosing HTTP Methods for REST API

Which HTTP method is the most appropriate for updating an existing resource completely in a REST API?

A PUT

B POST

C GET

D DELETE

💡 Hint

Consider which method replaces the entire resource at the given URI.

PUT is used to update or replace an existing resource completely. POST is usually for creating new resources, GET for retrieving, and DELETE for removing.

❓ scaling

advanced

Scaling REST APIs with Caching

Which caching strategy best improves REST API scalability by reducing server load for frequently requested data?

A Disable caching to always serve fresh data.

B Use client-side caching with cache-control headers and ETags.

C Store all responses permanently on the server without expiration.

D Cache only POST request responses on the client.

💡 Hint

Think about how HTTP headers help clients avoid unnecessary requests.

Client-side caching with cache-control headers and ETags allows clients to reuse responses when data hasn't changed, reducing server load and improving scalability.

❓ tradeoff

advanced

Tradeoffs in REST API Versioning

What is a common tradeoff when using URI versioning (e.g., /v1/resource) in REST API design?

A It eliminates the need for documentation since versions are clear in the URI.

B It allows seamless backward compatibility without any extra server maintenance.

C It forces clients to always use the latest API version without choice.

D It simplifies client requests but can lead to duplicated code and maintenance overhead on the server.

💡 Hint

Consider how versioning affects server code and client flexibility.

URI versioning makes it clear which API version is used but can cause duplicated endpoints and extra maintenance effort on the server side.

❓ estimation

expert

Estimating API Throughput for a High-Traffic REST Service

A REST API server handles 10,000 requests per second on average. Each request takes 50ms of server processing time. How many concurrent requests must the server handle to sustain this throughput without queuing?

A 500 concurrent requests

B 200 concurrent requests

C 50 concurrent requests

D 1000 concurrent requests

💡 Hint

Use Little's Law: Concurrent = Throughput × Latency.

Little's Law states that the number of concurrent requests equals throughput multiplied by average processing time. 10,000 req/s × 0.05 s = 500 concurrent requests.