API Developer Interview Questions for IT Hiring

Introduction

Hiring the right API Developer is critical for organizations that rely on reliable, scalable, and secure interfaces to connect systems, services, and clients. In the Information Technology industry, APIs are central to product integrations, partner connections, and internal platform development.

This guide provides structured interview questions for API Developer roles, including basic, intermediate, and advanced topics. It also includes five pre-screening one-way video interview prompts ideal for ScreeningHive to help teams speed up and standardize candidate evaluation.

API Developer Interview Questions

Basic API Developer Interview Questions

• What is the difference between REST and SOAP? Explain when you might choose one over the other.
• Describe the common HTTP methods and give an example use case for each.
• Explain the meaning of the HTTP status codes 200, 201, 400, 401, 403, 404, and 500.
• What are common authentication and authorization approaches for APIs, such as API keys, OAuth, and JWT?
• Compare JSON and XML as payload formats. What are the trade-offs?
• What does idempotency mean in the context of APIs and why is it important?
• Describe rate limiting and why it is applied to APIs.
• What is CORS and how does it affect API consumption from web browsers?

Intermediate API Developer Interview Questions

• You need to design a search endpoint that supports filtering, sorting, and pagination. How would you model the API and query parameters?
• Describe your approach to designing consistent error responses and how clients should handle them.
• How would you implement pagination for large result sets and what are pros and cons of offset versus cursor pagination?
• Explain caching strategies for APIs. Where would you apply caching and what headers or tools would you use?
• Walk through how you would secure an API that exposes sensitive user data to third-party clients.
• Describe how you would integrate with a third-party API that has unreliable performance or intermittent failures.
• How do you handle API versioning to avoid breaking existing clients while delivering new functionality?
• Explain your testing strategy for APIs, including unit, integration, and contract tests.
• How do you instrument APIs for logging and monitoring to support production troubleshooting?
• Describe a strategy to implement rate limiting and throttling that balances user experience and system protection.

Advanced API Developer Interview Questions

• Compare the roles of an API gateway and a microservices architecture. How do you decide which features to put in the gateway?
• When would you choose event-driven or message-based integration over synchronous REST calls? Provide architectural trade-offs.
• Discuss the use cases where GraphQL is a better fit than REST and potential pitfalls of adopting GraphQL.
• How do you profile and optimize API performance at scale? Provide examples of bottlenecks and remediation techniques.
• Design an authorization model for complex enterprise APIs that must enforce role based and attribute based access controls.
• Explain contract-first versus code-first API design. What are benefits and challenges of each approach?
• How do you manage backward compatibility across API releases and what strategies minimize client disruption?
• What considerations drive API SLAs and how do you design systems to meet those commitments?
• Describe how distributed tracing and correlation IDs help diagnose cross-service API issues in microservice environments.
• How do you lead API design reviews with cross functional teams to ensure quality, consistency, and security?

Pre-Screening Video Interview Questions for API Developer

These prompts are tailored for one-way video interviews on ScreeningHive. They are designed to quickly evaluate communication, technical depth, and problem solving before scheduling live interviews.

1. Briefly summarize your API development experience and the most significant API project you worked on.

   This question evaluates communication clarity, relevant experience, and ownership of past API work.

2. Describe a challenging API bug or outage you helped resolve. What steps did you take and what was the outcome?

   This question assesses troubleshooting ability, incident response process, and accountability under pressure.

3. Walk through how you would design an endpoint to support a new feature that returns user activity with filtering and sorting.

   This prompt gauges API design thinking, parameter modeling, and consideration of performance and client needs.

4. Explain the measures you would take to secure an API exposed to public clients and mobile apps.

   This evaluates knowledge of authentication, authorization, token handling, and best practices for protecting data.

5. Describe how you would investigate and fix a sudden performance regression in a production API.

   This question measures diagnostic approach, use of monitoring tools, and prioritization of fixes to restore service quality.

Conclusion

This collection of role specific questions helps hiring managers, recruiters, and HR teams evaluate API Developer candidates across foundational knowledge, practical skills, and advanced architecture and leadership topics. Candidates can also use these prompts to prepare for technical interviews.

ScreeningHive one-way video interviews make pre-screening faster and more consistent, enabling teams to standardize evaluations, reduce time to hire, and focus live interviews on the best qualified candidates.