Introduction
If you need to pass backend or QA interviews, mastering REST interview questions is the fastest way to show practical API knowledge and systems thinking. In the first 100 words you should be able to explain what REST is, common HTTP methods, status codes, and how to reason about idempotency and statelessness—core topics interviewers expect. This guide organizes the Top 30 Most Common REST interview questions you should prepare for into fundamentals, advanced concepts, testing and security, design patterns, and preparation strategies, with examples and references to authoritative resources to help you answer clearly and confidently. Takeaway: start with clarity on basics, then practice concise answers anchored in examples.
What are the core REST API fundamentals candidates must know?
A REST API is an architectural style for distributed hypermedia systems that relies on stateless operations over HTTP.
Explain that REST stands for Representational State Transfer, emphasize resources (URIs), use of standard HTTP verbs (GET, POST, PUT, PATCH, DELETE), and the importance of statelessness and clear status codes. Interviewers often test by asking how CRUD maps to HTTP verbs or why idempotency matters. Practical context: describe a simple resource like /users and how GET /users/123 returns a representation (JSON). For more study on core questions and examples, see resources like InterviewBit and GeeksforGeeks. Takeaway: answer fundamentals with definitions, verb mappings, and a concise example.
Technical Fundamentals
Q: What is REST?
A: REST is an architectural style using stateless HTTP methods to manage resources via representations like JSON.
Q: What are the common HTTP methods used in REST APIs?
A: GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS for resource retrieval and manipulation.
Q: What is statelessness in REST and why does it matter?
A: Each request contains all info needed; servers don't store client context, improving scalability and reliability.
Q: How do you map CRUD operations to HTTP verbs?
A: Create=POST, Read=GET, Update=PUT/PATCH, Delete=DELETE.
Q: What is a resource and how is it identified?
A: A resource is an abstraction (e.g., user) identified by a URI like /users/{id} and represented in JSON or XML.
Q: What are typical status codes you should mention in interviews?
A: 200 OK, 201 Created, 204 No Content, 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 500 Server Error.
Q: Why prefer JSON for REST APIs?
A: JSON is lightweight, language-agnostic, easy to parse, and widely supported by clients and tools.
Q: How is content negotiation handled?
A: Use Accept and Content-Type headers to negotiate representation formats like application/json or application/xml.
Which advanced REST concepts frequently separate junior from senior candidates?
Advanced REST interview questions test idempotency, versioning, HATEOAS, and when to use PUT vs PATCH.
Explain idempotency with examples (GET and PUT are idempotent; POST is not by default), compare full updates (PUT) to partial updates (PATCH), and introduce HATEOAS as a constraint that provides navigable links in responses. Tie answers to real trade-offs: complexity vs client flexibility. For deeper reading on advanced design and interview examples, check Merge.dev and Utkrusht.ai. Takeaway: show you can reason about trade-offs and when to apply each pattern.
Advanced Concepts
Q: What is idempotency in REST APIs?
A: Idempotency means multiple identical requests have the same effect as one; PUT is idempotent, POST typically is not.
Q: When should you use PUT vs PATCH?
A: Use PUT for full resource replacement, PATCH for partial updates to avoid resending unchanged fields.
Q: What is HATEOAS and why is it used?
A: HATEOAS embeds links in responses so clients discover actions dynamically, improving decoupling.
Q: How do you handle API versioning?
A: Use URI versioning (/v1/), header versioning, or content negotiation; choose based on compatibility and deployment needs.
Q: What is resource modeling in API design?
A: Define clear entities, relationships, and representations; avoid exposing internal models directly.
Q: How do you design for eventual consistency?
A: Use async patterns, event-driven updates, and communicate consistency guarantees in API docs.
Q: What is the difference between RPC-style endpoints and RESTful design?
A: RPC focuses on actions (verbs in URI), REST focuses on resources and standard HTTP semantics.
How should you answer REST API testing and security questions?
You should explain testing tools, test types, and common security practices concisely and with examples.
Mention Postman and automated suites (Rest Assured), cover unit vs integration vs contract tests, and outline security controls like HTTPS, OAuth2, API keys, rate limiting, and input validation. Reference testing guidance from GeeksforGeeks and Frugal Testing for tool-specific interview prep. Takeaway: combine tool knowledge with clear examples of tests and security trade-offs.
REST API Testing and Security
Q: How do you test a REST API manually?
A: Use Postman or curl to send requests, validate responses, headers, and status codes against expected behavior.
Q: What is contract testing and why is it important?
A: Contract tests verify that provider and consumer agree on request/response formats, preventing integration breaks.
Q: How do you secure REST APIs?
A: Use HTTPS, authentication (OAuth2/JWT), authorization, input validation, and rate limiting.
Q: What is CORS and how does it affect APIs?
A: Cross-Origin Resource Sharing controls browser access to resources; servers set CORS headers to allow trusted origins.
Q: How can you protect against common attacks like injection or CSRF?
A: Validate/sanitize input, use prepared statements, implement CSRF tokens, and enforce origin checks.
Which REST API design and architecture questions do interviewers ask at senior levels?
You should describe design patterns, microservices concerns, and API governance clearly and practically.
Discuss RESTful layering, API gateways, service decomposition, observability, and strategies for backward compatibility and versioning. Cite GitHub design question collections and Multisoft Systems for sample prompts. Emphasize trade-offs between simplicity and extensibility. Takeaway: demonstrate architectural thinking plus concrete examples.
Design and Architecture
Q: What is an API gateway and why use one?
A: An API gateway centralizes routing, authentication, rate limiting, and aggregation for microservices.
Q: How do you approach API versioning strategy?
A: Prefer backward-compatible changes, use semantic versioning, and choose URI or header strategies per client needs.
Q: What patterns help with large-scale REST systems?
A: Circuit breakers, bulkheads, retries with backoff, and idempotent endpoints for safe retries.
Q: How do you document REST APIs?
A: Use OpenAPI/Swagger with examples, schemas, and clear error codes for discoverability and client generation.
Q: What is pagination and which strategies exist?
A: Pagination limits response size; use offset-based, cursor-based, or keyset pagination depending on performance needs.
How should candidates prepare and which tools are commonly discussed in interviews?
You should prepare a checklist: fundamentals, advanced topics, testing tools, live coding, and mock interviews.
Practice concise answers to the Top 30 Most Common REST interview questions you should prepare for, implement small sample APIs, write Postman collections, and run contract tests with frameworks like Rest Assured. Use structured study from InterviewBit and Merge.dev for common prompts and Frugal Testing for tool-focused prep. Takeaway: practice both verbal answers and hands-on tasks until explanations link to demonstrations.
Preparation Strategies and Tools
Q: What is the best way to prepare for REST interview questions?
A: Build sample APIs, practice mapping scenarios to HTTP methods, and rehearse concise trade-off explanations.
Q: Which tools should you know for REST testing?
A: Postman, curl, Rest Assured, and API mocking tools for integration tests.
Q: How do you demonstrate troubleshooting in an interview?
A: Explain debugging steps: reproduce, inspect logs, validate request/response, and test fixes.
Q: What should be in your REST interview checklist?
A: HTTP basics, status codes, idempotency, versioning, security, testing tools, and sample endpoints.
Q: How can mock servers help during preparation?
A: Mock servers let you simulate APIs and practice clients, contract tests, and error scenarios.
How Verve AI Interview Copilot Can Help You With This
Verve AI Interview Copilot gives structured, context-aware feedback on REST interview questions, helping you refine explanations, practice live answers, and simulate follow-ups. Use targeted prompts to improve clarity on idempotency, versioning, or security, get suggested sample code snippets, and rehearse concise responses for behavioral or technical follow-ups. The tool adapts to your role and level, highlights gaps in explanations, and helps reduce interview anxiety by giving instant corrective cues. Try Verve AI Interview Copilot to practice answers, review sample API scenarios, and track progress with simulated interviews using Verve AI Interview Copilot. Get role-specific prompts and real-time clarity from Verve AI Interview Copilot.
What Are the Most Common Questions About This Topic
Q: Can Verve AI help with behavioral interviews?
A: Yes. It applies STAR and CAR frameworks to guide real-time answers.
Q: Where can I practice REST interview coding tasks?
A: Use local projects, Postman, and mock servers for hands-on practice.
Q: Which resource lists common REST questions?
A: InterviewBit and GeeksforGeeks have curated REST interview lists.
Q: Should I memorize status codes?
A: Memorize common ones and explain others by category (2xx, 4xx, 5xx).
Q: Is Postman enough for testing interviews?
A: Postman is great; add automated tests and contract testing for depth.
Conclusion
Preparing the Top 30 Most Common REST interview questions you should prepare for means combining clear definitions, trade-off reasoning, testing know-how, and architecture thinking. Structure answers around a definition, a concise example, and the trade-offs or alternatives—this builds confidence and clarity. Try Verve AI Interview Copilot to feel confident and prepared for every interview.