API Developer Interview Questions

Looking for an API Developer to join your team? Revelo can help you source and vet top-tier candidates.

 Job description
 Interview questions

Table of Contents

Hiring an API developer requires a thorough vetting process to ensure you are hiring someone with the right technical skills and capabilities needed and that they are a good fit for your team and culture. It is a process that requires a keen understanding of the technical skills involved and an in-depth assessment of soft skills, personality traits, and professional demeanor. 

Interviews are the perfect avenue for this comprehensive evaluation, allowing you to gauge a candidate's ability to design, develop, and maintain APIs. Preparing for such an interview requires a strategic approach, but Revelo can help by sourcing potential candidates, arranging interviews, and guiding you through the interview process.

As a start, this article will provide valuable resources to help you hire API developers. You will gain insights into the key responsibilities of an API developer and explore a range of API developer interview questions and answers tailored for entry-, mid-, and senior-level candidates. 

What Is an API Developer?

An API developer, or application programming interface developer, is a specialized software engineer who designs, builds, and maintains APIs. APIs are the backbone of many modern digital services, serving as the communication protocols that allow different software applications to interact. They enable smooth data transfer between systems, enabling various software components to work together seamlessly. They are essential in creating scalable, reliable, and cohesive software solutions that can interact with other systems.

API developers typically work on projects that involve creating new API documentation for specific use cases or improving existing APIs for better performance and compatibility. They may also design and implement integrations of third-party APIs into a software system.

You may need to hire an API developer if your organization wants to build or enhance software applications that need to interact effectively with a web service or other systems. This could involve anything from developing a mobile app that needs to access server-side resources to creating a web application that relies on data from multiple sources.

Entry-Level API Developer Interview Questions 

An entry-level API developer may be the ideal fit if you need someone to assist with basic API development tasks. The candidate may not have much experience at this stage but should still possess the fundamental knowledge and skills to contribute to your team. Therefore, the API developer interview questions you ask should focus on gauging the candidate's understanding of basic API development concepts while allowing them to demonstrate their passion and enthusiasm for learning new skills.

Below are a few entry-level API developer interview questions you can use.:

Explain what an API is and why it is important.

While this is one of the most basic API developer interview questions, it is also one of the most important. The candidate's answer should provide adequate detail by explaining that an API is a set of functions and procedures that allow two software applications to interact in an organized manner.

What is your experience with programming languages commonly used in API?

This question will reveal the candidate's familiarity with programming languages like JavaScript, Python, Java, and Ruby. The ideal candidate should have some experience with these languages and be able to explain how they have used them in previous projects.

How do you ensure the security of an API?

API security is essential for keeping data safe and secure. The candidate should be aware of common security measures such as encryption, TLS, authorization methods, and API keys. They should also explain how they implement these measures in their development process. For instance, they might mention using tools such as OAuth for authentication or JWT for authorization.

What do you consider when designing an API?

This question will provide insight into the candidate's design approach and methodology. The answer should include API goals and objectives, data models, authentication protocols, scalability issues, functionality, error-handling strategies, and performance optimization techniques.

Mid-Level API Developer Interview Questions 

For roles that require more experience, you should look for mid-level API developers who can handle complex tasks. These candidates must understand the fundamentals and more advanced concepts, including API design principles, authentication protocols, development frameworks, software testing, UI testing, and debugging techniques.

When interviewing a mid-level API developer, consider asking the following questions.

What is the difference between a REST API and a SOAP API?

Representational State Transfer (REST) and Simple Object Access Protocol (SOAP) are the API architectures most commonly used. The candidate's ideal answer should mention REST APIs being lightweight and using simple HTTP method calls, whereas SOAP API is more complex and uses XML to exchange data between applications.

How have you handled versioning in APIs in your previous roles? Can you give an example?

This API developer interview question tests the candidate's ability to strategically plan and manage changes over time while minimizing user disruption. It's also an opportunity to gauge their familiarity with different versioning strategies—such as URI versioning, parameter versioning, or header versioning—and their ability to choose the most appropriate one, depending on the situation or functionality needed.

A satisfactory answer to this question should explain an experience where versioning was necessary, their strategy, and how they managed the transition to ensure minimal impact on end-users.

Describe a time when you had to troubleshoot a complex issue with an API.

Troubleshooting issues with APIs is a common task for API developers, and it can often involve intricate and nuanced problems that require a deep understanding of the API, its integration points, testing tools, and its underlying technologies.

This question is pivotal for assessing a candidate's problem-solving skills, resilience, and experience addressing complex technical challenges. Troubleshooting issues with APIs is a common task for API developers, and it can often involve intricate and nuanced problems that require a deep understanding of the API, its integration points, and the underlying technologies.

What does "stateless" mean in the context of REST APIs?

This question is fundamental when assessing the candidate's understanding of REST architectural styles. An ideal answer should demonstrate that the candidate understands that in a stateless REST API, each request from a client to a server must contain all the information needed to understand and process the request.

What are status codes in HTTP? Give examples of different codes and what they mean.

Asking this question helps assess the candidate's knowledge of HTTP status codes and their significance in API development. It also provides insights into their experience with debugging API responses and their ability to handle different scenarios while interacting with APIs.

The candidate should, therefore, explain that HTTP status codes are standard response codes given by website servers on the internet, and they help identify the cause of the problem when a web page or other resource does not load properly. They should also mention HTTP status codes, such as '200' for a successful HTTP request, '404' if a resource is not found, '500' for an internal server error, etc.

Senior-Level API Developer Interview Questions 

Interviewing for a senior-level API developer position requires a comprehensive assessment of the candidate's skills, experiences, reliability, and leadership capabilities. Besides their mastery in API development, you will want to gauge their ability to make strategic decisions, manage projects, and promote teamwork.

Here are some questions when interviewing for a senior-level API developer position.

How do you document your APIs for use by other developers? Can you share any best practices?

When asking this question, you're not just looking at the candidate's ability to write code but also their ability to communicate complex technical information. You're gauging their attention to detail, understanding of the user's perspective, and commitment to creating a seamless developer experience.

A strong answer will include the candidate detailing their approach to documenting APIs, including all necessary elements like endpoints, methods, parameters, sample requests and responses, and error codes. They might also share some best practices like keeping the documentation up-to-date, making it easily accessible, using clear and concise language and providing real-world examples.

Have you ever had to persuade stakeholders or team members to use an API solution? How did you go about it?

This question is crucial when determining the candidate's communication and persuasion skills, which are vital when influencing decision-making processes and aligning everyone toward a common goal. The candidate should describe the situation, the resistance they faced, how they presented their case, and the eventual outcome. For instance, the candidate could mention using technical data, cost-benefit analysis, demonstrations, or solutions aligned with strategic objectives to present their case. 

What strategies do you use when mentoring or coaching junior developers?

In a senior-level position, the candidate will likely be responsible for guiding junior developers, helping them improve their skills, and fostering a supportive learning environment.

A strong answer should involve the candidate discussing their strategies for mentoring junior developers, such as setting clear expectations, providing constructive feedback, encouraging continuous learning, fostering a culture of curiosity and experimentation, and leading by example. They should also discuss how they tailor their approach based on individual needs and learning styles.

Hire API Developers With Revelo

While API developer interview questions are an important part of the hiring process, they are only as effective as the overall recruitment strategy. To recruit API developers efficiently, you must understand their skills, experiences, and motivations.

At Revelo, we make it easy for companies to hire highly qualified developers. Our platform connects you with experienced engineers who match your technical requirements, time zone alignment, and language proficiency needs. We also assist with payroll, benefits administration, taxes, and local compliance adherence, providing a comprehensive solution for your hiring needs.

Contact Revelo today, and let us help you find the right API developers for your team.

Why Choose Revelo?

Quick turnaround for candidate shortlists

A vast talent pool of 
pre-vetted developers

Professional sourcing, vetting, and onboarding support

Hire Developers
Adriana G.
This is some text inside of a div block.
11 years
Hire Developers

Stay in the loop! 📩 Join our newsletter for the latest updates, trends, and innovations in HR technology.

Subscribe and be the first to hear about our new products, exclusive content, and more.

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.