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50 REST API Design interview questions

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Core REST API Fundamentals

  1. What is a REST API?
  2. What are RESTful web services?
  3. Explain the core principles of REST architecture.
  4. Difference between REST and SOAP.
  5. What are resources in REST?
  6. What is statelessness in REST APIs?
  7. Role of HTTP in REST APIs.
  8. List common HTTP methods and their usages.
  9. Difference between PUT, POST, and PATCH.
  10. What is idempotency? Why does it matter?

REST API Mechanics & Design

  1. What are URI and URL?
  2. Best practices for naming REST endpoints.
  3. How to version a REST API?
  4. What is content negotiation?
  5. How do APIs handle filtering, sorting, and pagination?
  6. What are HTTP status codes and when to use them?
  7. What is HATEOAS and why is it used?
  8. Explain caching and cache control headers in REST.
  9. How does REST pattern support layered architecture?
  10. What is uniform interface constraint?

Error Handling & Responses

  1. How should REST APIs handle errors?
  2. What are common error response formats?
  3. Difference between 4xx and 5xx errors.
  4. What is a 204 No Content response and when to use it?
  5. How to design meaningful error payloads?

Security & Authorization

  1. Common authentication mechanisms in REST (JWT/OAuth2/API key).
  2. Difference between authentication vs authorization.
  3. How do you secure REST APIs?
  4. What are rate limits and rate limiting strategies?
  5. How to handle CORS issues?

Performance, Caching & Scalability

  1. How to implement caching in REST?
  2. Explain ETag and When-None-Match for conditional requests.
  3. How to minimize latency in REST APIs?
  4. How to implement pagination for large datasets?
  5. Designing for scalability in RESTful systems.

Data Formats & Serialization

  1. Common data formats in REST (JSON vs XML).
  2. Why JSON is widely preferred?
  3. What is media type versioning?
  4. How to support multiple representation formats?
  5. Handling large payloads or streaming. (common interview design topic)

Testing, Documentation & Best Practices

  1. How to test REST APIs? (manual, automated, tools)
  2. Best practices for REST API documentation.
  3. What is OpenAPI/Swagger and why use it? (common MNC topic)
  4. What are API mocks and stubs? Why are they used?
  5. Definition and use of API contracts. (common interview area)

Real-World Design & Architecture

  1. How would you design a REST API for an e-commerce catalog? (practical task)
  2. Design a rate-limited REST service for public users. (scenario question)
  3. Walkthrough a white-board REST API design task. (from interviewee experience)
  4. Handling backward compatibility when evolving APIs.
  5. Tradeoffs between REST and GraphQL for API design. (common advanced Q)

Tips for answering these questions in MNC interviews:

  • Always relate answers to real-world use cases (mobile apps, microservices)
  • Explain why design decisions are made
  • Use examples with HTTP methods, endpoints, status codes, and sample payloads