2026

API Design Interview Questions 2026

A current, 2026 snapshot of the API Design interview questions worth knowing — kept up to date as frameworks and best practices evolve, so you prepare with what companies are actually asking in 2026.

60Questions14Beginner13Intermediate33Senior

60 API Design questions

  1. 1Explain Content Negotiation (Accept headers).Intermediate
  2. 2What is a Webhook?Intermediate
  3. 3Designing Error Responses in APIs.Intermediate
  4. 4What is HATEOAS?Intermediate
  5. 5How to design a Paginated API?Intermediate
  6. 6What is Rate Limiting and why is it necessary?Intermediate
  7. 7Explain OAuth2 and JWT for API security.Intermediate
  8. 8What is Idempotency in APIs?Intermediate
  9. 9How to handle API Versioning?Intermediate
  10. 10REST vs. GraphQL: When to use which?Intermediate
  11. 11Difference between Public and Private APIs?Beginner
  12. 12What is an API Key?Beginner
  13. 13What is Statelessness in REST?Beginner
  14. 14What is API Documentation?Beginner
  15. 15Explain the difference between Query Parameters and Path Parameters.Beginner
  16. 16What is an API Endpoint?Beginner
  17. 17What is JSON and why is it used in APIs?Beginner
  18. 18What are HTTP Status Codes?Beginner
  19. 19Explain the common HTTP Methods.Beginner
  20. 20What is a RESTful API?Beginner
  21. 21API Design Interview Question 1 (Free)Beginner
  22. 22API Design Interview Question 5 (Free)Intermediate
  23. 23API Design Interview Question 4 (Free)Beginner
  24. 24API Design Interview Question 3 (Free)Senior
  25. 25API Design Interview Question 2 (Free)Intermediate
  26. 26Service Discovery and Load Balancing in API NetworksSenior
  27. 27Designing Search APIs with Elasticsearch/SolrSenior
  28. 28Security: Rate Limiting vs Throttling vs QuotasSenior
  29. 29API Testing Strategies: Contract Testing (Pact)Senior
  30. 30Idempotent API design in high-concurrency environmentsSenior
  31. 31Governance and Life Cycle Management of APIsSenior
  32. 32Designing an API for Mobile Clients (BFF Pattern)Senior
  33. 33Graceful Degradation and Priority-based SheddingSenior
  34. 34Shadow APIs and Zombie APIs: Risk MitigationSenior
  35. 35API Observability: Metrics, Logs, and Health ChecksSenior
  36. 36Designing long-running operations (Async Request-Reply)Senior
  37. 37Database Per Service vs. Shared Database in API designSenior
  38. 38API Performance: Payload compression and serialization (Protobuf)Senior
  39. 39Global Latency Optimization (Edge APIs and CDNs)Senior
  40. 40Evolutionary API Design: Avoiding Breaking ChangesSenior
  41. 41Designing Multi-tenant APIs and data isolationSenior
  42. 42CQRS (Command Query Responsibility Segregation) in API designSenior
  43. 43Handling Thundering Herd Problem in APIsSenior
  44. 44Designing an API for Third-party Ecosystems (SDKs/DevEx)Senior
  45. 45Zero-Trust Architecture in API SecuritySenior
  46. 46GraphQL Schema Stitching vs. FederationSenior
  47. 47Designing an Event-Driven API with Kafka/RabbitMQSenior
  48. 48API Caching Strategies: Client, Proxy, and Server-sideSenior
  49. 49Idempotency Keys and Distributed LockingSenior
  50. 50Distributed Tracing in complex API ecosystemsSenior
  51. 51gRPC vs REST for internal service communicationSenior
  52. 52Circuit Breaker Pattern in API designSenior
  53. 53Designing for 99.999% Availability in APIsSenior
  54. 54Microservices Communication: Synchronous vs. AsynchronousSenior
  55. 55Architecture of an API GatewaySenior
  56. 56API Design Advanced Interview Question 10Beginner
  57. 57API Design Advanced Interview Question 9Senior
  58. 58API Design Advanced Interview Question 8Intermediate
  59. 59API Design Advanced Interview Question 7Beginner
  60. 60API Design Advanced Interview Question 6Senior

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Frequently asked questions

Are these API Design interview questions up to date for 2026?

Yes. This page reflects 60 API Design interview questions kept current with today's frameworks, tooling and interview trends, with each answer maintained and dated.

What API Design topics should I focus on in 2026?

Prioritise the fundamentals plus the modern patterns interviewers ask about now. Each question here includes a detailed answer, code example and common mistakes so you can target the highest-impact areas.

Are these questions free?

You can read the question and a short answer for free. A subscription unlocks the full detailed explanation, real-world example, common mistakes and follow-up questions for each one.