The Kotlin programming language was developed by JetBrains with coding performance, code safety, and developer satisfaction in mind. Since its release in 2011, Kotlin has become a favorite language of developers and has replaced Java in many projects.
In this in-depth guide, we look at Kotlin developer hiring options and their average salaries and share interviewing tips. We also discuss the benefits of using the language and how world-renowned companies have incorporated Kotlin into their projects.
What Is Kotlin Used For
Kotlin is a simple and type-safe language that supports asynchronous programming techniques and is used for mobile app development, web front-end development, server-side applications, and data science.
Due to Kotlin’s popularity, Google increased support for the language in 2019, making it the preferred language for Android app developers. Android Studio, Google’s Android operating system IDE, officially started supporting Kotlin with Android Studio 3.
Kotlin supports type-safe builders and delegated properties. These innovative language features help build easy-to-use abstractions.
The coroutines in Kotlin help create server-side applications that scale to a huge number of clients with modest hardware requirements. Kotlin also supports the gradual migration of large codebases from Java to Kotlin. The team can start writing new code in Kotlin while keeping the older parts of its system in Java.
Web Front-end Development
Kotlin for Data Science
Kotlin integrates with interactive editors, such as Jupyter Notebook and Apache Zeppelin to help engineers explore and visualize data, share findings with the team, or develop skills in data science and machine learning.
The Kotlin community also created an ecosystem of libraries for data-related tasks such as mathematical operations over multidimensional arrays, training deep learning models, and natural language processing.
Multi-platform Mobile Development
Kotlin Multiplatform Mobile SDK helps engineers to maintain a single codebase for networking, data storage, analytics, and algorithms of Android and iOS apps. Teams can also use Kotlin as a single language for both cross-platform and native applications because Kotlin syntax follows the same concepts used in iOS development.
Advantages of Kotlin
- Kotlin is a modern, concise, and safe language
It combines all the best bits of imperative, object-oriented, and functional programming. The language has a modern syntax and some new ideas like coroutines it brings to current Java web development.
Kotlin is clean and more readable as JetBrains estimates indicate approximately a 40% cut in the number of lines of code compared to Java. It also features various type systems to eliminate problems such as NullPointerException.
- Compatible with the Java ecosystem
Kotlin is designed to interoperate fully with Java, and developers can easily call existing Java code from Kotlin, as well as Kotlin code from Java. This makes adoption much easier and less risky.
Moreover, developers can use both Kotlin and Java sources in the same project in IntelliJ IDEA. The IDE also includes a plugin that automatically converts Java files to Kotlin.
- Kotlin is multiplatform
Multiplatform developers will focus more on building a product on different platforms than on learning different languages. They can use Kotlin Multiplatform to share the same code across Android, iOS, and web applications. This will reduce the amount of business logic coded by front-end developers and minimize coding and testing efforts.
- Community support
Kotlin is an open-source language with over 450 contributors, including 90 JetBrains developers. It evolves with the help of its vibrant community, which includes 200 Kotlin User Groups, 37,000 Kotlinlang Slack users, and other members spread across Kotlin’s forum, subreddit, and YouTube channel.
Are Kotlin Developers in Demand?
Kotlin is the 6th most wanted technology according to the 2022 Stack Overflow Developer Survey involving 71,000 respondents. The survey also shows that the median yearly salary for Kotlin programmers rose from $55,000 in 2021 to $69,000 in 2022.
Since 2019, Kotlin has also been one of the top 20 languages, according to RedMonk, which compiles the rankings based on GitHub pull requests and Stack Overflow discussions.
However, demand for Kotlin developers does not only depend on the language knowledge. It is more critical to have engineering experience that will help programmers become intuitive about designing. Companies will prioritize developers who are relevant to their field and are interested in solving architectural problems, and Kotlin will be one of those tools.
In fact, the language is used by development teams in well-known companies such as Google, Amazon, Philips, and Netflix. Google also made Kotlin a “first class” language for developing Android applications.
Expertise Required from Kotlin App Developers
Senior Kotlin developers should have a solid foundation in the language, as well as extensive experience in Java and Android-based development. They must have a thorough understanding of object-oriented programming concepts and their implementation, and a proven track record of frequent software delivery to production. They should also be highly knowledgeable about the mobile app ecosystem, including front-end components and server-side frameworks.
Some companies also prefer candidates with a bachelor’s degree or equivalent experience in computer science.
While these may vary depending on project requirements, in general, Kotlin programmers should have the following skills:
- Strong knowledge of Kotlin and Java
- Experience in Android app development and Android Studio
- Practical experience in mobile applications architecture, flow, design, implementation, and deployments to app stores
- In-depth understanding of design fundamentals, object-oriented programming concepts, and architecture principles
- Familiarity with Agile development concepts, CI/CD pipelines, and DevOps practices
- Understanding of version control systems and platforms
Companies typically expect software developers to be self-disciplined, open to feedback, continually strive for improvement and have good communication skills.
Being a great team player makes a developer’s job more exciting and makes people more likely to help them in the future. In addition, being able to empathize with the team allows them to predict how others are likely to react, meaning that the developer can tailor how they communicate with others. Coming up with new ideas is much easier when there is an understanding between team members, when no one expects negative feedback or mockery, no matter how someone feels about an idea.
Developers should also be able to speak clearly and confidently, listen actively, and avoid interrupting others. These qualities are usually a sign that the developer is an effective communicator — a characteristic that an employer may have already noticed during the interview.
Where to Hire Kotlin Developers
Employers can use different models for hiring Kotlin developers: freelance, in-house hiring, project outsourcing, or hiring a contractor. In this section, we’ll take a look at the highlights of each model.
Depending on the hiring model, we also suggest a list of groups, job boards, and communities for Kotlin engineers. These links will guide employers on where to post jobs, find contractors, or visit communities to connect directly with the most active users.
Hiring freelancers is suitable for short-term projects, small tasks, and companies with limited budgets. In contrast to in-house engineers and contractors, freelancers are often responsible for several jobs, and the quality of their output could be subpar to that of a client’s specifications. Furthermore, because these developers are often juggling multiple projects, employers don’t have the same control over a freelancer as they do with a contractor or in-house employee.
Tech companies hire full-time, in-house employees to build their core team and culture. In addition, in-house staff members tend to be more motivated — they explore a product in detail because they are committed to developing it and growing the company.
Companies can hire in-house engineers by hosting or attending hackathons and tech conferences. They can also request an in-house engineer from a headhunter.
Finally, employers search their local market by utilizing their HR services. For example, browsing LinkedIn profiles, searching for talent in communities, or posting a Kotlin engineer job on an online board is a good starting point.
Remember, though, job boards were invented during the Great Depression when millions of people were out of work and there was a talent surplus. There is no talent surplus in today’s job market, so simply posting a job opening may not attract the most desired professionals.
In-house Hiring: Job-boards
Communities and Groups
- Official Kotlin community portal
- Kotlin user groups on the Awesome Kotlin portal
- Kotlin groups on Meetup
Tech companies use this hiring strategy when focusing on their core business aspects by assigning entire projects to outside development services managed by their CTO or product owner from the in-house team.
Outsourcing companies, like any employer, carry risks; however, they are much more selective, unlike freelance platforms. However, outsourcing limits communication between the company and external providers as you will not manage each member of the extended team directly.
Hiring a Contractor (Staff Augmentation)
Staff augmentation on-demand uses full-time employed software engineers from outsourcing agencies. However, unlike assigning or handing over an entire project to an outsourcing company, employers manage remote developers and communicate with them directly.
Also, employers don’t need to bother with retirement contributions or paying for health insurance, bonuses, vacations, office rental, or workstations as they do for in-house employees. The hiring process, in this case, is faster since the developers are already employed, their skills and experience are verified, and the company does not need to talk about the benefits package.
- Companies can hire contractors with Kotlin expertise on YouTeam.
Kotlin Developer Salary
According to the 2022 Stack Overflow Developer Survey, the average annual salary for Kotlin programmers is $69,000. This number includes bonuses and benefits before taxes and deductions.
Kotlin Developer Salaries are Location Dependent
We’ve compiled information on the average salaries of Kotlin engineers on Glassdoor. Please note that the platform took into account the earnings of engineers with varying degrees of expertise, meaning that actual salaries may differ from case to case.
These numbers represent the median incomes as reported by Glassdoor’s proprietary Total Pay Estimate model based on salaries collected from platform users. Wages in India, the United States, Canada, and the United Kingdom consist of a base salary and additional pay, which may include a cash bonus, commission, tips, and profit sharing.
|Country||Salary per year, USD*|
*According to Glassdoor
Kotlin Contractor Hourly Rates
The above table is more relevant for companies that plan to hire in-house and are interested in annual salaries. However, if you are open to remote work and are considering hiring a contractor, this section contains developer hourly rates in different countries.
|Min, USD*||Median, USD*||Max, USD*|
*According to YouTeam
|Country||Average hourly rate, USD*|
*According to YouTeam
Kotlin Developer Interview Questions
Companies usually have a standardized interviewing process to evaluate candidates better. They prepare a list of the most important questions to cover and draft possible answers. The interview can start with general questions about education and work experience.
The employer can then ask about the candidate’s professional qualities and recent achievements in Kotlin programming, using the following questions:
- What are you looking for in your next position?
- What are your best professional qualities?
- What was your recent professional achievement using Kotlin programming language? Are there any projects in which you have been particularly successful?
- How long would it take you to learn a new tool or build a skill set?
- What Kotlin features do you find difficult to use?
Finally, the employer can discuss the engineer’s understanding of Kotlin technical details. For example:
- What Kotlin features can help you write better code?
- What are the advantages of Kotlin versus Java? What are Kotlin’s drawbacks?
- Explain the concept of null safety in Kotlin.
- What are the different types of constructors available in the language?
- What do you know about function extension in the context of Kotlin?
- What are Kotlin coroutines good for?
- Is Kotlin better than Java?
Unlike Java, Kotlin requires less code, supports coroutines, and offers different type systems to eliminate problems like NullPointerException. The language also allows the developer to extend the functionality of classes without having to inherit from the class.
- Does Kotlin have a future?
The future of mobile and web development is usually difficult to predict, but the Kotlin community is optimistic about the language’s ongoing development. Kotlin is currently the preferred language for Android development and is officially supported by Spring, the most popular Java backend development framework in enterprise companies.
The key priorities the Kotlin team is investing the most effort into include making the change-test-debug cycle faster, rewriting the language compiler optimized for speed, concurrency, and unification, and expanding support for server-side use cases across the Kotlin ecosystem.
- What are Kotlin’s disadvantages?
Anything you can do in Java can be done in Kotlin, but the reverse is not always true. Stack Overflow users reported the limitations in interoperability between Java and Kotlin. They claim it’s hard for Java to implement Kotlin suspend functions. Similarly, the programmer might not be able to call inline functions from Java, name parameters, and omit them to get their default values.
- Is Kotlin frontend or backend?
Developers widely use Kotlin for both front-end and backend development. In addition to its widespread use on Android, Kotlin is suitable for building scalable server-side applications. Spring introduced a dedicated Kotlin support with Spring Framework 5.0. Since then, Spring has translated all of its documentation to Kotlin and added built-in support for Kotlin-specific features such as coroutines.
In addition to Spring, JetBrains has released Ktor, a Kotlin-first framework for building web applications.
Well-known Companies Using Kotlin
In this section, we learn about how well-known companies implemented Kotlin in their projects. Each of them pointed out the advantages of Kotlin in its concise and easy-to-read syntax, asynchronous capabilities, and seamless interoperability with Java.
Sixty (60) Google applications, including Maps, Home, Play, Drive, and Messages, are built using Kotlin. One example where engineers have benefited from using Kotlin’s features comes from the team behind the Google Home app. Since they started to incorporate Kotlin into their codebase, the team reported a 33% decrease in NullPointerExceptions, the most common crash type on Google Play Console. Engineers also claim that using data classes and the Parcelize plugin has cut the number of Google Home app code lines by 80% compared to Java.
Amazon has decided to use Kotlin to develop microservices designed to support Prime Video profiles. This led to a more concise, more readable code base compared to Java and left less room for bugs. The adoption of Kotlin has also increased application throughout and improved developer satisfaction.
Netflix Studios has experimented with a multiplatform architecture while building Prodicle, a production-facing mobile app. They used Kotlin Multiplatform to maintain a single codebase for the business logic of iOS and Android apps. The team wrote platform agnostic logic once and then compiled it to a Kotlin library for Android and a native Universal Framework for iOS.
In 2019, Atlassian announced that it would use Kotlin for all new Jira services as interoperability with Java was one of its strong points, and the language has already been established in developer communities. The company claimed Kotlin came in handy when they needed to decompose an application into multiple services to scale it better. Moreover, Atlassian learned they could hire a Java developer and turn them into a Kotlin developer in just one week, and the teams using Kotlin are more productive.
All new code in the Trello Android application is written in Kotlin as well.
Philips used Kotlin Multiplatform for its cloud solution, the HealthSuite Digital Platform. Their team was able to push out new features faster and the codebase was easier to maintain. The company also discovered that integrating Kotlin Multiplatform has improved interaction and knowledge sharing between the Android and iOS developers on the team.