REST API Developer Interview Questions

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

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 Interview questions

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To create an app, you need REST application programming interface (API) developers. These programmers can create top REST APIs, interfaces used by two computer systems to exchange data securely over the web. Most software and applications need APIs to communicate with third-party and internal applications to perform various tasks. For instance, your internal accounts system must use a web API to share data with users' banking systems to generate monthly payslips.

However, hiring REST API developers can be time-consuming and expensive, especially if you're unfamiliar with REST API skills. Continue reading to learn about REST API developers and the best entry-, mid-, and senior-level REST API developer interview questions. 

What Is a REST API Developer?

A REST API developer is a programmer who works with REST or RESTful APIs. RESTful APIs are built on REST, which stands for representational state transfer. REST is an architectural style that imposes conditions on how APIs should work.

Initially created as a guideline to manage communication on complicated networks like the web, REST services have the following principles:

  • Statelessness is a communication method where the client stores and handles session-related information independently. As such, REST clients can perform a POST request to get resources in any order, and every request is separate from other requests.
  • Uniform interface means clients and the server are separate. This separation means that clients are not concerned with data storage and client code portability is improved.
  • Layered architectural systems means clients can connect to other intermediaries between the client and server. Servers can also pass requests in order to send a data request to other servers. 
  • Cacheability is the ability to store responses on an intermediary or client to improve server response time.

Most REST API developers have the following skills:

  • Experience with an API automated testing tool and API development
  • Bachelor's or master's degree in information technology, computer science, or engineering
  • Knowledge of REST API design patterns, status codes, POST method, and HTTP protocol
  • Familiarity with Java, J2ee, and Core Java
  • Mentorship and leadership skills (for mid-level and senior developers)

REST API developers work in various industries, including software development, finance, manufacturing, and eCommerce. Duties depend on the employer, but most companies hire REST API developers for the following:

  • Analyze, develop, design, and implement REST APIs
  • Perform feasibility and definition analysis
  • Apply the latest software design techniques 
  • Implement APIs based on architecture frameworks and guidelines
  • Write clean and maintainable object-oriented code
  • Identify and fix problems throughout the software development lifecycle

Entry-Level REST API Developer Interview Questions

Entry-level REST API developers are usually fresh college or boot camp graduates. They have basic programming skills and must be familiar with code versioning tools such as Git. They should also be passionate about learning REST API development from senior colleagues. As an employer, you should look for junior devs who are honest about what they don’t know, stay positive despite challenges, have a strong desire to learn, and share your company’s values.

When hiring entry-level REST API developers, you should prepare interview questions that assess applicants' foundational programming and RESTful API skills. Here are some top REST API interview questions and answers to ask junior developers.

What makes RESTful web services unique?

This question assesses applicants' core understanding of RESTful APIs. 

A good answer should state that RESTful web services follow REST architecture and principles, such as statelessness, uniform interface, layered system, and cacheability. It should also mention that RESTful web services are unique because they provide scalability, maintainability, and support communication among different programming languages and applications. 

What is URI?

This question also assesses prospective hires' understanding of REST APIs. A strong candidate should begin by mentioning that URI stands for Uniform Resource Identifier. They should then explain that URIs are used to ensure each resource is identified within the REST architecture and that there are two types of URIs:

  • Uniform Resource Locator (URL) fetches a resource from its location. They start with a protocol such as HTTP or FTP.
  • Uniform Resource Name (URN) identifies the resource by a unique and persistent name. URN names usually start with URN. For example, urn:isbn:[ISBN number] identifies a book based on its ISBN.

What programming languages are you familiar with?

This open-ended question reveals candidates' familiarity with API programming languages. REST API programmers should be familiar with several object-oriented programming languages, including Flask, Python, Express, and Node. 

Mid-Level REST API Developer Interview Questions

Mid-level REST API developers typically have four to six years of working experience. They are responsible for mentoring and leading entry-level developers, developing and supporting application development, conducting code reviews, and optimizing API programming. When looking for a mid-level REST API developer, look for the ability to analyze and apply the proper solutions to the problems at hand, a solid knowledge of your company’s preferred programming languages, robust communication and leadership skills, and awareness of the industry’s best coding practices.

Mid-level REST API developer interview questions should assess candidates' understanding of REST architectural API programming best practices and leadership skills. Here are some commonly asked REST API interview questions for a candidate interested in a mid-level developer position. 

What are the best practices for developing RESTful web services?

This question tests applicants' ability to apply RESTful development best practices. A strong answer should mention at least three of the following best practices:

  • Develop REST APIs that respond and accept JSON data formats. Most REST server and client technologies have built-in support for JSON objects. 
  • Use the nesting in the endpoint's naming convention to represent the resource hierarchy. This makes it easier to retrieve the data of one object that is located in another object.
  • Use plural nouns when naming resource endpoints. Names containing verbs tend to be more confusing because HTTP requests already mention what the request is doing in its HTTP method or verb. Commonly used HTTP methods for defining verbs include PUT, GET, POST, and DELETE.
  • Error handling should return appropriate error codes and messages to help developers take corrective actions. However, you should not make the messages too detailed. The more detailed the messages, the more information hackers have for hacking your application.
  • Use pagination and filtering when retrieving massive amounts of resources on the server. Returning huge amounts of data simultaneously can slow down the system and reduce application performance.

How would you mentor an entry-level REST API developer?

This question tests applicants' ability to lead and mentor entry-level colleagues. The best candidate should be compassionate, humble, knowledgeable, and passionate about leadership and mentorship. They should also prioritize mentoring, establish a road map for mentoring, be tolerant of mistakes, and assign level-appropriate projects.

What are the best practices for creating URIs for web services?

Ask this question to evaluate applicants' understanding of URI best practices. A good answer should demonstrate a solid understanding of URI creation best practices, such as:

  • Use plural nouns when defining resources.
  • Maintain backward compatibility when developing URI.
  • Use forward slashes to indicate the hierarchy between the collections and the resources.
  • Although URIs are case-insensitive, you should only use lowercase.
  • Use appropriate HTTP methods such as DELETE, GET, PATCH, and PUT.

Senior-Level REST API Developer Interview Questions

Senior-level REST API developers have over six years of working experience. They are familiar with best practices, automation, code correction, and leading teams. 

When hiring senior-level REST API developers, be sure to test their advanced programming and communication skills. You should also assess their ability to communicate with stakeholders and the C-suite. Here are commonly asked API interview questions for experienced developers.

What are idempotent methods?

This technical question tests applicants' understanding of idempotent, which refers to an operation's ability to be applied multiple times without changing the result. 

A good answer must mention the importance of developing idempotent APIs while designing REST APIs. Without idempotent APIs, end-users can write client-side code that can lead to duplicate and erroneous responses. The answer should also mention that REST provides in-built idempotent methods, such as GET, HEAD, DELETE, PUT, and TRACE.

What are the differences between SOAP and REST?

Ask this question to assess whether a potential hire understands when to use REST. 

The ideal answer should mention that Simple Object Access Protocol (SOAP) is an approach to API design that is highly structured and uses XML data format. In contrast, REST is more flexible and lets applications exchange data in various formats. It should also mention other differences between SOAP and REST, such as:

  • SOAP reads can't be cached, while REST read requests can be.
  • SOAP has strict standards that must be followed, while REST's standards don't need to be strictly followed.
  • SOAP is slower, while REST is faster.
  • SOAP is used when reliability is essential and stateful data transfer is required. Because REST services are scalable and maintainable, developers use them most of the time.

How do you explain REST API development concepts to the C-suite?

This question tests applicants' communication skills. Your team's best senior-level REST API developer must explain complicated REST API development concepts to the C-suite so they can make business decisions.

Answers should highlight the candidate's ability to summarize complicated ideas and presentation skills. For instance, a strong candidate may mention using an infographic, animation, or dashboard to explain the pros and cons of implementing a new REST API tool. 

Hire REST API Developers With Revelo

Finding the right REST API developer can be challenging. To hire the right candidate effectively and efficiently, you must create a strong hiring process that emphasizes technical skills and increases the need for soft skills as the role becomes more senior. 

Revelo can help you create this hiring process. As Latin America's leading tech talent marketplace, we can connect you with time-zone-aligned systems engineers who have been rigorously vetted for technical skills, soft skills, and English proficiency. Our team can also manage payroll, benefits, taxes, and compliance adherence throughout the hiring process.

Interested in seeing how we can help? Contact Revelo to start hiring today.

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Eduarda B.
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10 years
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