REST API Interview Questions and Answers 2026 - Top 10 Web API Design Questions
REST API Interview Questions and Answers 2026 - Top 10 Web API Design Questions
03-21-2026, 09:58 AM
Keywords: REST API interview questions 2026, API design interview, HTTP methods interview, RESTful services interview, web API interview
1. What is REST and what are its core principles?
REST (Representational State Transfer) is an architectural style for distributed systems. Core principles include statelessness, client-server separation, uniform interface, cacheability, layered system, and optional code on demand. RESTful APIs use HTTP methods and follow resource-based URL patterns.
2. Explain HTTP methods: GET, POST, PUT, PATCH, and DELETE.
GET retrieves resources without side effects. POST creates new resources. PUT replaces an entire resource. PATCH partially updates a resource. DELETE removes a resource. GET and DELETE have no request body. PUT and POST are not idempotent. GET, PUT, and DELETE are idempotent.
3. What are HTTP status codes and their categories?
1xx are informational responses. 2xx indicate success: 200 OK, 201 Created, 204 No Content. 3xx are redirections. 4xx are client errors: 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found. 5xx are server errors: 500 Internal Server Error, 503 Service Unavailable.
4. How do you design RESTful URL patterns?
Use nouns for resources, not verbs. Use plural names for collections. Nest related resources logically. Use query parameters for filtering, sorting, and pagination. Keep URLs lowercase with hyphens. Version APIs in the URL or headers. Examples: /api/v1/users, /api/v1/users/123/orders.
5. What is the difference between authentication and authorization in APIs?
Authentication verifies identity using credentials like API keys, JWT tokens, or OAuth. Authorization determines what an authenticated user can access based on roles and permissions. Authentication answers who you are, authorization answers what you can do. Both are essential for API security.
6. Explain API rate limiting and throttling.
Rate limiting restricts the number of API requests a client can make within a time window. Implement using token bucket or sliding window algorithms. Return 429 Too Many Requests when exceeded. Include rate limit headers: X-Rate-Limit, X-Rate-Remaining, X-Rate-Reset. Essential for preventing abuse.
7. What is API versioning and what strategies exist?
API versioning manages breaking changes while maintaining backward compatibility. Strategies include URL path versioning (/api/v2/), query parameter versioning (?version=2), header versioning (Accept-Version: v2), and content negotiation. URL versioning is most common and easiest to implement.
8. How do you handle pagination in REST APIs?
Offset-based pagination uses page and limit parameters. Cursor-based pagination uses a pointer to the last item, better for large datasets. Keyset pagination uses the last record's key. Return total count, next/previous links, and current page metadata. Cursor-based prevents skipping issues.
9. What is the difference between REST and GraphQL?
REST uses multiple endpoints for different resources with fixed data structures. GraphQL uses a single endpoint where clients specify exact data needs. REST can over-fetch or under-fetch data. GraphQL solves this but adds complexity. REST is better for simple CRUD, GraphQL for complex data requirements.
10. How do you secure a REST API?
Use HTTPS for all communications. Implement JWT or OAuth 2.0 for authentication. Validate and sanitize all inputs. Apply rate limiting and throttling. Use CORS properly. Implement API keys for identification. Log and monitor API access. Use parameterized queries to prevent injection attacks.
Conclusion: REST API knowledge is fundamental for every developer in 2026. Master API design principles, security, pagination, and versioning to ace your interviews.
Tags: #RESTAPI #InterviewQuestions #APIDesign #Backend #WebDevelopment #HTTP #GraphQL #API2026
REST APIs are the foundation of modern web communication in 2026, used by every web and mobile application worldwide. Whether you're preparing for a Backend Developer, API Engineer, or Full-Stack Developer role, these top 10 REST API interview questions will help you succeed.
Keywords: REST API interview questions 2026, API design interview, HTTP methods interview, RESTful services interview, web API interview
1. What is REST and what are its core principles?
REST (Representational State Transfer) is an architectural style for distributed systems. Core principles include statelessness, client-server separation, uniform interface, cacheability, layered system, and optional code on demand. RESTful APIs use HTTP methods and follow resource-based URL patterns.
2. Explain HTTP methods: GET, POST, PUT, PATCH, and DELETE.
GET retrieves resources without side effects. POST creates new resources. PUT replaces an entire resource. PATCH partially updates a resource. DELETE removes a resource. GET and DELETE have no request body. PUT and POST are not idempotent. GET, PUT, and DELETE are idempotent.
3. What are HTTP status codes and their categories?
1xx are informational responses. 2xx indicate success: 200 OK, 201 Created, 204 No Content. 3xx are redirections. 4xx are client errors: 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found. 5xx are server errors: 500 Internal Server Error, 503 Service Unavailable.
4. How do you design RESTful URL patterns?
Use nouns for resources, not verbs. Use plural names for collections. Nest related resources logically. Use query parameters for filtering, sorting, and pagination. Keep URLs lowercase with hyphens. Version APIs in the URL or headers. Examples: /api/v1/users, /api/v1/users/123/orders.
5. What is the difference between authentication and authorization in APIs?
Authentication verifies identity using credentials like API keys, JWT tokens, or OAuth. Authorization determines what an authenticated user can access based on roles and permissions. Authentication answers who you are, authorization answers what you can do. Both are essential for API security.
6. Explain API rate limiting and throttling.
Rate limiting restricts the number of API requests a client can make within a time window. Implement using token bucket or sliding window algorithms. Return 429 Too Many Requests when exceeded. Include rate limit headers: X-Rate-Limit, X-Rate-Remaining, X-Rate-Reset. Essential for preventing abuse.
7. What is API versioning and what strategies exist?
API versioning manages breaking changes while maintaining backward compatibility. Strategies include URL path versioning (/api/v2/), query parameter versioning (?version=2), header versioning (Accept-Version: v2), and content negotiation. URL versioning is most common and easiest to implement.
8. How do you handle pagination in REST APIs?
Offset-based pagination uses page and limit parameters. Cursor-based pagination uses a pointer to the last item, better for large datasets. Keyset pagination uses the last record's key. Return total count, next/previous links, and current page metadata. Cursor-based prevents skipping issues.
9. What is the difference between REST and GraphQL?
REST uses multiple endpoints for different resources with fixed data structures. GraphQL uses a single endpoint where clients specify exact data needs. REST can over-fetch or under-fetch data. GraphQL solves this but adds complexity. REST is better for simple CRUD, GraphQL for complex data requirements.
10. How do you secure a REST API?
Use HTTPS for all communications. Implement JWT or OAuth 2.0 for authentication. Validate and sanitize all inputs. Apply rate limiting and throttling. Use CORS properly. Implement API keys for identification. Log and monitor API access. Use parameterized queries to prevent injection attacks.
Conclusion: REST API knowledge is fundamental for every developer in 2026. Master API design principles, security, pagination, and versioning to ace your interviews.
Tags: #RESTAPI #InterviewQuestions #APIDesign #Backend #WebDevelopment #HTTP #GraphQL #API2026
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