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How to Hire Kotlin Developers

Vetting Kotlin Developers: Job Description & Interview Questions

Over the past 20 years, my business partners and I have hired hundreds of different types of programmers for many different software companies. Through this experience, it’s safe to say we’ve gained plenty of knowledge regarding the dos and don’ts of hiring the right programmers for the job.

Here’s a checklist to reference the next time your company needs to hire a Kotlin programmer.

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What is Kotlin Used For?

Kotlin is a cross-platform programming language developed by JetBrains. It has grown considerably in the past few years and is a popular language for mobile app development. Here are some common uses of the Kotlin programming language.

Android App Development

In 2019, Google announced that Kotlin is now the preferred language for developing Android mobile apps. It is thought to be used by over 70% of the top 1000 apps on the Play Store. Many developers prefer Kotlin for app development as it provides extra code safety features, developers can achieve more in fewer lines of code.

Website Back-Ends

47% of Kotlin developers are now using the language for the back-ends of websites. This means that Kotlin is being used to handle the logic behind websites such as Google, Amazon, Shazam, and Gradle.

What to Look for When Hiring a Kotlin Developer

When hiring a Kotlin programmer, there are a few things you have to consider including experience, rates, and the type of work arrangement. It also depends on the type of project you have and what skills you need to complete it.

Kotlin Required Skills

Here are some of the basic skills that a Kotlin Developer is expected to have:

  • Procedural programming
  • Lambda functions
  • Null safety
  • Kotlin as a scripting language
  • Objects, classes, and abstract classes

Java Experience

Kotlin developers should have some experience with the following:

  • Android app development
  • Website back-end scripting
  • Data storage on memory-limited devices
  • Object-oriented programming (OOP)
  • Functional programming
  • The unique features of the Java Virtual Machine (JVM)
  • Kotlin’s standard library and the Java Class Library
  • Testing and debugging Kotlin programs
  • Enterprise, commercial, and open-source projects

How to Write a Kotlin Developer Job Description

Writing the perfect Kotlin job description is essential to ensure that you can attract the top developers. It's also important to ensure that you set the proper expectations up-front to streamline the vetting process, saving everyone time and money.

Kotlin Developer Job Description Template

Company Introduction

Use this section to write 2-3 sentences about your company. Make sure to provide information about the company culture and benefits. This would be a good section to link to your company website. The best candidates will do some advanced research.

Job Description

We are looking for a Kotlin developer who has an appetite for solving complex problems and building seamless user interactions to a world-class standard. As a Kotlin developer, you will be creating fast, fluid, reliable, and responsive mobile applications for our users.


  • Write code for new mobile apps
  • Work with stakeholders to create software requirements
  • Write test code and develop test plans for apps
  • Optimize code for usability, speed, and efficiency
  • Help maintain code quality, organization, and automatization
  • Add other responsibilities here that are important for the project/job


  • Strong proficiency in Kotlin, including functions in the standard library
  • Prior experience developing mobile applications
  • Knowledge of the Java Virtual Machine (JVM)
  • Understanding of null safety, and how to use it in Kotlin
  • Understanding of object-oriented programming (OOP) and inheritance
  • A structured approach to systems analysis and development
  • Familiarity with related languages such as Java {{if_required}}
  • Exposure to databases {{if_required}}
  • Cloud platforms such as AWS or Azure {{if_required}}
  • Writing unit tests and integration tests
  • Understanding of code versioning tools such as Git
  • Familiarity with agile development techniques
  • Strong communication skills
  • Specify other frameworks, libraries, or any other technology relevant to your project/job
  • Education level or certification requirements

Kotlin Interview questions

When looking to hire a Kotlin developer, consider asking some of the following interview questions:

  • Why is Kotlin preferred for app development over Java or JavaScript?
  • What is a data class in Kotlin?
  • What is the difference between var and val?
  • How is null safety performed in Kotlin?
  • What are coroutines and how are they used?
  • What are some of the disadvantages of Kotlin?
  • When would an Array be used instead of a List?
  • What is the difference between open and public in Kotlin?
  • What is the init block in Kotlin?
  • How can builder patterns be implemented in Kotlin?
  • How can Singleton classes be created?
  • Is there a static keyword in Kotlin?
  • What is the difference between launch/join and async/await in coroutines?

Freelance Kotlin Developer Rates

The average salary for a Kotlin developer is $127,500 per year in the United States. When hiring a Kotlin freelancer, you can expect to pay $36.58 on average per hour. Kotlin freelancer rates can range from $15-$60 per hour depending on the developer's experience, where they are located, their availability, and other programming languages required.

Check out our detailed pricing guide for more freelance developer rates.

Where to Hire a Kotlin Developer – Top Websites

Read our list of the top websites to hire a Kotlin developer.

Developer Hiring Guides

If you are looking for other types of technical talent, we’ve put together hiring guides for these technologies as well.

Programming Languages
Top Programming Languages
Frontend Frameworks
Top Frontend Frameworks
Backend Frameworks
Top Backend Frameworks
Content Management Systems
Content Management Systems
  • Unity
  • Salesforce
  • iOS / Android


Where can I find a Kotlin developer?

There are many places where you can find and hire a Kotlin developer online. If you're looking for a full-time developer, you can try popular job boards like Indeed and LinkedIn. For the best freelancers, consider using a remote hiring platform focused on placing programmers like Upstack or Toptal. You can also find Kotlin developers on general freelancing marketplaces like Upwork and Fiverr.

How much does it cost to hire a Kotlin developer?

The average salary for a Kotlin developer is $127,500 per year in the United States. When hiring a Kotlin freelancer, you can expect to pay $36.58 on average per hour. Kotlin freelancer rates can range from $15-$60 per hour depending on the developer's experience, where they are located, their availability, and other programming languages required.

What are the most important skills to look for in a Kotlin developer?

As there are multiple different paradigms for developing Kotlin applications, developers should have skills in procedural, object-oriented, and functional programming. They should know about null safety and how to work with the Java Virtual Machine (JVM).

What does a Kotlin developer do?

Kotlin developers design and develop programs in the Kotlin programming language. These programs are usually, but not limited to, Android apps. In addition to programming, continued development, and optimization, they will also be required to fix bugs in existing code, and test new code before it is released to the public.