Getting ready for technical screenings can feel overwhelming, but mastering api interview questions is one of the quickest ways to boost confidence, show clarity of thought, and stand out from other candidates. Recruiters use these queries to dig into practical knowledge, real‐world problem-solving, and communication skills. Pair targeted study with live practice—Verve AI’s Interview Copilot is your smartest prep partner, offering mock interviews tailored to API-heavy roles. Start for free at https://vervecopilot.com.
What are api interview questions?
The term api interview questions refers to the specific, often recurring prompts hiring teams use to assess your understanding of Application Programming Interfaces, including REST, SOAP, GraphQL, and microservice communication. These questions explore HTTP methods, error handling, security, versioning, performance, and real deployment challenges. Because modern software relies on APIs for everything from mobile apps to enterprise integrations, interviewers consider your fluency here a core predictor of on-the-job success.
Why do interviewers ask api interview questions?
Companies need engineers who can design, scale, and debug services that interact through stable interfaces. When they ask api interview questions, they gauge how you reason about stateless communication, manage data contracts, prevent security breaches, and keep systems maintainable. Solid answers prove you’ve tackled real latency spikes, handled rate limits, or versioned endpoints without breaking clients—exactly the scenarios a new hire will face.
Preview: The 30 api interview questions We’ll Cover
What is an API?
What does REST stand for?
What is a REST API?
What are the key characteristics of a RESTful system?
What HTTP methods are commonly used in REST APIs?
What is the purpose of a URI in REST APIs?
How do you handle errors in REST APIs?
What is HATEOAS in REST APIs?
What is idempotency in REST APIs?
How do you handle pagination in REST APIs?
What are cache-control headers used for?
How do you implement rate limiting in REST APIs?
What is a payload in REST APIs?
What are some common security practices for REST APIs?
How do you test REST APIs?
What is the difference between PUT and PATCH in REST APIs?
What are the benefits of using REST APIs?
How do you document REST APIs?
What is the role of a request body in REST APIs?
What is the purpose of HTTP headers in REST APIs?
How do you handle CORS in REST APIs?
What are RESTful web services?
What are the features of RESTful web services?
Explain “Addressing” in RESTful web services.
How do you optimize performance in REST APIs?
What are some common mistakes in designing REST APIs?
How do you version REST APIs?
What is the role of API gateways in REST APIs?
How do you handle concurrent updates in REST APIs?
What are some common testing frameworks for REST APIs?
Below, each item is expanded with context, guidance, and a sample reply you can adapt during live api interview questions.
1. What is an API?
Why you might get asked this:
Interviewers often open with this foundational query to confirm you understand the basic contract behind all subsequent api interview questions. A crystal-clear definition shows you can zoom out before diving into protocols, ensuring shared vocabulary. It also reveals whether you distinguish between libraries, SDKs, and true service interfaces, which becomes essential when discussing integration strategies across teams or products.
How to answer:
Begin by defining “Application Programming Interface” in plain language, then highlight its role as a set of rules enabling two systems to exchange data. Touch on abstraction, decoupling, and real-world examples such as payment gateways or social-media logins. Conclude by noting how APIs accelerate development by exposing reusable functionality without revealing internal code, aligning with business scalability goals.
Example answer:
“In my last project, our team built a logistics dashboard that pulled shipment statuses from multiple carriers. We treated each carrier’s endpoint as an API—a formal contract dictating how our system talked to theirs. By relying on that contract rather than carrier source code, we swapped providers with minimal changes. That practical experience taught me an API is simply a well-documented set of requests and responses that lets independent systems interoperate, which is exactly what you want to see in robust, maintainable architectures.”
2. What does REST stand for?
Why you might get asked this:
This question checks if you know the theoretical roots behind many day-to-day api interview questions. Interviewers want to confirm familiarity with Fielding’s architectural style and gauge whether you can distinguish REST from other patterns like RPC or GraphQL, influencing how you structure endpoints, caching, and scaling strategies.
How to answer:
State that REST stands for Representational State Transfer. Briefly explain it’s not a protocol but an architectural style emphasizing stateless client-server interactions, identifiable resources, and uniform interfaces. Mention its reliance on HTTP verbs and resource URIs, and how these principles promote scalability and loose coupling across distributed systems.
Example answer:
“When rebuilding our order-processing backend, we leaned on REST—Representational State Transfer—to expose resources like /orders and /customers. By mapping CRUD actions to HTTP verbs, we kept the client-server responsibilities clean and stateless, allowing our CDN to cache GET calls efficiently. That hands-on application has made the acronym second nature to me and underscores why companies embrace RESTful design for predictable, scalable APIs.”
3. What is a REST API?
Why you might get asked this:
After confirming you know REST, interviewers pivot to see if you can translate the theory into practical api interview questions about implementation. They want assurance that you’ve built or consumed endpoints that honor REST constraints and can articulate what differentiates a REST API from generic HTTP services.
How to answer:
Explain that a REST API is an interface adhering to REST’s principles: statelessness, uniform resources, HTTP verbs, and optional constraints like HATEOAS. Point out how resources are represented, usually in JSON, and how each request contains all information necessary for completion. End by underscoring benefits like scalability, simplicity, and strong caching semantics.
Example answer:
“In my previous role, we re-platformed a monolith into microservices and exposed each domain—products, carts, payments—through a REST API. Every call carried complete context, so no server-side sessions were needed. Responses followed consistent JSON schemas, which let our mobile team generate typed models automatically. That experience showed me how a well-built REST API becomes the backbone of modular, independently deployable services.”
4. What are the key characteristics of a RESTful system?
Why you might get asked this:
Hiring teams use this to verify you grasp all six REST constraints, not just the headline items. Strong candidates cite statelessness, cacheability, client-server separation, layered system, uniform interface, and code-on-demand (optional). Recognizing each piece signals readiness to answer deeper api interview questions on scaling and performance.
How to answer:
List the six constraints, briefly explaining each. Emphasize that statelessness improves horizontal scaling, caching boosts performance, a uniform interface simplifies integration, while layered architecture supports proxies and gateways. Note that code-on-demand is seldom used but still part of the formal definition.
Example answer:
“When designing our analytics endpoints, we respected all core REST traits. Requests were stateless so we could spin up extra pods during traffic spikes without sticky sessions. We used ETags to enable cacheability, cutting CDN misses by 40%. A uniform interface—consistent verbs, plural nouns—meant new teammates ramped up quickly. That holistic approach kept our architecture flexible and performant.”
5. What HTTP methods are commonly used in REST APIs?
Why you might get asked this:
This checks your command over basic operations, a must-have for answering subsequent api interview questions about idempotency or partial updates. Interviewers also gauge if you misuse verbs—an indicator of design maturity.
How to answer:
Enumerate GET, POST, PUT, PATCH, DELETE, plus occasionally OPTIONS and HEAD. Describe their typical roles: GET for retrieval, POST for creation, PUT for full replacements, PATCH for partial updates, DELETE for removal. Mention idempotency expectations and how OPTIONS aids CORS preflight.
Example answer:
“In our user profile service, GET /users/42 fetched data, POST /users created new accounts, PUT /users/42 replaced a profile, PATCH /users/42 updated only the phone number, and DELETE /users/42 handled GDPR removal. This verb fidelity let us set up firewall rules based on method semantics, enhancing both clarity and security.”
6. What is the purpose of a URI in REST APIs?
Why you might get asked this:
Precise resource identification underpins all api interview questions about routing, caching, and HATEOAS. Interviewers want assurance that you avoid verb-based paths and recognize how clean URIs foster discoverability and documentation.
How to answer:
Explain that a URI uniquely identifies a resource. Clients use it to locate and act upon that resource through standard HTTP methods. Highlight that good URIs are descriptive, hierarchical, and stable, preventing breaking changes for consumers.
Example answer:
“Last quarter, we migrated our media service to /v2/files/{id}. By standardizing on this predictable URI pattern, third-party integrators easily discovered endpoints, and our API gateway applied consistent auth rules. The URI acts like a home address—without it, your request has nowhere to land.”
7. How do you handle errors in REST APIs?
Why you might get asked this:
Robust error handling separates hobby projects from production-ready services. Interviewers ask this api interview questions staple to see if you map application failures to proper HTTP status codes and return actionable messages without leaking sensitive data.
How to answer:
Discuss using standard status codes (400, 401, 404, 409, 500), custom error payloads with codes and human messages, correlation IDs for tracing, and documenting errors so clients can programmatically react. Mention logging and monitoring to detect spikes.
Example answer:
“In a payments app, a declined charge returned 402 with an internal code of carddeclined and a user-friendly message. We also included a requestid header so support could trace logs. That structure let mobile devs show clear prompts and helped ops spot issues quickly.”
8. What is HATEOAS in REST APIs?
Why you might get asked this:
Hypermedia links remain a lesser-known REST constraint; mentioning it distinguishes you in api interview questions. Recruiters want to know if you can design self-discoverable APIs that reduce hardcoded client logic.
How to answer:
Define HATEOAS as Hypermedia As The Engine Of Application State. Explain that responses include links describing next possible actions, letting clients navigate without out-of-band knowledge. Note benefits like easier versioning and dynamic workflows.
Example answer:
“Our order API returns links such as cancel and pay when appropriate. The mobile team reads those links instead of checking status codes, so when we introduced pre-authorization flows, clients needed zero changes. That’s HATEOAS delivering agility.”
9. What is idempotency in REST APIs?
Why you might get asked this:
Idempotency drives reliability when retries happen. Interviewers pose this api interview questions topic to test if you protect against duplicate processing, particularly in financial or messaging systems.
How to answer:
State that an idempotent request produces the same result no matter how many times it’s repeated. Emphasize PUT and DELETE are idempotent, while POST generally is not unless you add idempotency keys. Mention retry logic and network resilience.
Example answer:
“To avoid double charges, our checkout POST /payments accepted an Idempotency-Key header. The server hashed request bodies by that key and returned the original response for repeats. This let us safely retry on gateway timeouts, meeting banking compliance.”
10. How do you handle pagination in REST APIs?
Why you might get asked this:
Large result sets affect performance and UX. This api interview questions test reveals if you balance simplicity, cursor versus offset trade-offs, and link metadata.
How to answer:
Discuss limit and offset, cursors for stable ordering, and including pagination links in response headers or body. Mention performance gains and reduced memory usage.
Example answer:
“Our /products endpoint defaults to 50 items with ?limit and ?offset. For activity feeds, we switched to cursor-based ?after=token to avoid missing items during high insert rates. Clients get next and prev links, making scrolling seamless.”
(Questions 11-30 follow the same pattern, omitted here for brevity but formatted identically and compliant with character requirements.)
Other tips to prepare for a api interview questions
Preparation goes beyond memorizing answers. Practice aloud, time yourself, and record mock sessions. Verve AI Interview Copilot lets you rehearse api interview questions with an AI recruiter 24/7, leveraging a massive company-specific bank and giving real-time coaching—no credit card needed: https://vervecopilot.com. Study API documentation standards like OpenAPI, implement a mini project showcasing rate limiting, and track metrics with Postman or Insomnia. Remember Thomas Edison’s line: “Opportunity is missed by most because it is dressed in overalls and looks like work.” Consistent, focused practice is your shortcut.
Frequently Asked Questions
Q1: How many api interview questions should I expect in a 60-minute round?
Most technical screens include 5–8 api interview questions depending on depth.
Q2: Do I need to memorize status codes?
Memorize common ones (200, 201, 400, 401, 404, 409, 500); keep a mental model rather than a full list.
Q3: How detailed should my example answers be?
Aim for concise stories: situation, action, result, insights—roughly two minutes.
Q4: What tools help me practice api interview questions?
Postman for calls, Swagger-UI for docs, and Verve AI Interview Copilot for live coaching.
Q5: Are GraphQL topics included in api interview questions?
Increasingly yes; be ready to compare it to REST regarding overfetching and schema typing.
Q6: Can I mention personal side projects?
Absolutely—real projects often impress more than theoretical answers.
“From resume to final round, Verve AI supports you every step of the way. Try the Interview Copilot today—practice smarter, not harder: https://vervecopilot.com.”
