REST API Interview Questions Interview Questions and Answers

REST API Interview Questions Interview Questions and Answers

Practice every question in this topic using expandable answers and interview tips. Answer aloud first, then open the explanation.

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Q1. What is REST? [Easy]

Answer: REST (Representational State Transfer) is an architectural style for designing distributed web services. It relies on standard HTTP protocols, utilizing methods like GET, POST, PUT, and DELETE to manage resources.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q2. What are the common HTTP methods used in REST? [Easy]

Answer: The primary HTTP methods are GET (retrieve data), POST (create new data), PUT (replace data entirely), PATCH (partially update data), and DELETE (remove data).

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q3. What is meant by "Statelessness" in REST? [Medium]

Answer: Statelessness means the server does not store any client context or session data between requests. Every request from the client must contain all the information necessary for the server to process it.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q4. What is the difference between PUT and PATCH? [Medium]

Answer: PUT is used to replace an entire resource with a new payload (and may create it if it doesn't exist). PATCH is used to apply partial modifications to an existing resource without altering other fields.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q5. What is Idempotency in REST APIs? [Hard]

Answer: An idempotent operation produces the same result on the server regardless of how many times it is executed. Methods like GET, PUT, DELETE, and HEAD are idempotent, whereas POST is not.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q6. Explain the common HTTP status code categories. [Easy]

Answer: 1xx (Informational), 2xx (Success, e.g., 200 OK, 201 Created), 3xx (Redirection), 4xx (Client Error, e.g., 400 Bad Request, 401 Unauthorized, 404 Not Found), and 5xx (Server Error, e.g., 500 Internal Server Error).

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q7. What are the core constraints of a RESTful API? [Medium]

Answer: The six core constraints are: Client-Server architecture, Statelessness, Cacheability, Uniform Interface, Layered System, and Code on Demand (which is optional).

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q8. What is HATEOAS? [Hard]

Answer: HATEOAS (Hypermedia As The Engine Of Application State) is a REST constraint where the client interacts with the application entirely through dynamic hypermedia links provided by the server in its responses.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q9. How do you handle API versioning in REST? [Medium]

Answer: API versioning can be handled in multiple ways: URI path versioning (e.g., /api/v1/users), Query parameters (?version=1), Custom Request Headers (x-api-version: 1), or Content Negotiation (Accept header).

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q10. What is the difference between REST and SOAP? [Medium]

Answer: REST is a lightweight architectural style using HTTP and typically JSON. SOAP is a strict protocol relying exclusively on XML, requiring more bandwidth but offering built-in security and compliance standards (WS-Security).

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q11. How do you secure a REST API? [Hard]

Answer: REST APIs are secured using HTTPS (TLS/SSL) for encryption in transit, robust authentication (like JWT, OAuth 2.0, or API Keys), role-based authorization, rate limiting, and input validation to prevent injections.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q12. What is CORS? [Medium]

Answer: CORS (Cross-Origin Resource Sharing) is a security mechanism enforced by browsers. It allows a server to specify which external domains (origins) are permitted to access its REST API resources.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q13. What is a URI and a URL in REST? [Easy]

Answer: A URI (Uniform Resource Identifier) identifies a resource (e.g., /users/123). A URL (Uniform Resource Locator) is a specific type of URI that also provides the means to locate it (e.g., https://api.example.com/users/123).

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q14. How should filtering, sorting, and pagination be handled? [Medium]

Answer: They are typically handled using URL query parameters to keep the base endpoint clean. For example: /users?role=admin&sort=name_asc&page=2&limit=50.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Q15. What is a REST API payload? [Hard]

Answer: The payload is the actual data pack sent in the body of the HTTP request or response. In REST, payloads are typically formatted in JSON or XML, representing the state of the resource being transferred.

Interview tip: Define it clearly, give a small example, and mention one practical use or limitation.

Study checklist

Explain the answer without reading.
Write one small example.
Compare framework or database version differences in official documentation.

REST API Interview Questions Interview Questions and Answers

Practice one question at a time. Read the question, answer aloud, then compare your explanation with the answer.

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Study method: define the concept, give a small example, and mention one practical use or limitation.