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The ultimate guide for hiring Kotlin developers
A preferred language for Android apps, Kotlin offers many benefits: concise syntax, extra safety features, and full interoperability with Java. With the growing demand for Kotlin developers comes the need to find the right talent for your projects.
We know this process well. We receive over 2.2 million applications annually and have hired only the top 1% of LATAM tech professionals. Our experience in recruiting top-notch developers has allowed us to create this guide to help you with your hiring process too.
Finding skilled Kotlin app developers is crucial for your project’s success and your company’s growth. The process involves more than just technical skills, though. It’s also about finding candidates who fit in with your team and can drive innovation within your company’s dynamics. This guide includes key skills and practical interview questions with example answers. We’ll help you make better-informed decisions and find the best Kotlin developers for your team.
Before you start hiring
Culture fit
When hiring Kotlin developers, first assess how well they will fit into your company culture. To do that, you need to identify your company’s core values and evaluate the work environment. From there, look for candidates who align with these principles. A developer who shares your company’s mission and fits well with your team’s dynamics will work better together and for the long term. This will ultimately lead to better project results.
Modernization
Consider your project’s modernization needs and the role of a Kotlin developer in your organization. Then, look for candidates with expertise in modern technologies and practices such as reactive programming, microservices architecture, and cloud-native development. A developer who can update legacy systems and integrate new solutions will keep your organization competitive and innovative in a fast-paced tech environment.
Collaborative mindset
Kotlin developers often need to work closely with other team members and key stakeholders. Look for candidates who have demonstrated the ability to work in team settings and communicate with non-technical stakeholders. They should be able to explain complex ideas clearly and work harmoniously with other developers, product managers, and other organizational members. A collaborator will create a cohesive team environment.
Industry experience
Prioritize Kotlin developers who have experience in your industry. Industry knowledge brings valuable insights and a deeper understanding of the challenges and regulatory requirements your organization faces on a daily basis. A developer with industry experience will deliver more tailored and effective solutions with less trial and error. They already have the experience that has informed their decisions and can better align with your business objectives and industry standards.
Adaptability
Adaptability is key for Kotlin developers. Especially in the fast-paced world of software development. Look for candidates who have demonstrated flexibility in learning new tools, frameworks, and methodologies. An adaptable developer can quickly adjust to project changes, regulatory changes, and the latest technological advancements. They should be able to handle the dynamic nature of Kotlin development and continue to contribute to your team regardless of the ups and downs.
16 skills every Kotlin developer should have
Kotlin is a modern, statically typed programming language. It has gained popularity for Android development in particular. That’s because of its concise syntax, extra safety features, and full interoperability with Java. These features make it perfect for building high-performance applications and allow developers to write cleaner and more maintainable code. The features ultimately reduce the likelihood of common programming errors. Read: Increased productivity.
With coroutines for asynchronous programming and extensive support for functional programming paradigms, Kotlin has a versatile toolbox for building many types of applications. A good Kotlin developer combines technical skills with soft skills to drive project success. They should be proficient in Kotlin-specific frameworks, libraries and tools and able to build and maintain high-quality, scalable applications. But soft skills are just as important to fit into team environments and drive innovation. By leveraging their technical expertise and interpersonal skills, Kotlin developers can boost project outcomes.
Here are the technical and soft skills a Kotlin developer should have to contribute to your organization’s growth and success.
Technical skills to look for in your ideal Kotlin developer
1. Java interoperability
Kotlin is fully interoperable with Java. Kotlin developers must be able to integrate and work with Java code in a Kotlin project, migrate projects from Java to Kotlin, and access Java libraries and frameworks.
2. Android app development
Since Kotlin is an official language for Android development, developers working with the language must have experience with Android. This includes knowledge of Android Software Development Kit (Android SDK), Android Jetpack components, Android Studio, and Android UI design principles and patterns.
3. Backend development
Knowledge of backend development helps a Kotlin developer. It allows them to use Kotlin features in backend frameworks like Ktor and Spring and develop more efficiently.
4. Object-oriented programming and functional programming
Understanding object-oriented and functional programming allows developers to fully leverage Kotlin’s features. The multi-paradigm language supports both OOP and FP and by choosing the right approach for the context developers can write more efficient and maintainable code.
5. Build tools and dependency management
Kotlin developers use build tools like Gradle and Maven to automate project setup, compilation, and packaging. These tools maintain consistency, reproducibility, and smooth integration with CI/CD pipelines.
6. Version control
Version control systems like Git help to strengthen collaboration, change tracking, branching and merging, code backup, and continuous integration. These are key practices for your projects.
7. Testing
Kotlin developers need to catch bugs early and ensure code quality and maintainability. They should be familiar with unit testing frameworks like JUnit and Kotlin Test and understand UI testing with Espresso or UI Automator for Android.
8. Continuous integration/continuous deployment (CI/CD)
Understanding CI/CD pipelines and tools like Jenkins, CircleCI, and GitHub Actions is crucial to improving code quality, speeding up deployment, and ensuring consistency.
9. Database management
Kotlin developers should be good at database management to ensure offline access, scalability, data security, and offline access. They should know SQL and have experience with relational databases like SQLite and PostgreSQL.
10. Networking
Experience with HTTP, REST, WebSocket, Retrofit, and Ktor helps to exchange data and enhance functionality and overall user experience. Networking also supports features like cloud storage and social media integration.
11. Security
Hire Kotlin app developers who have a deep understanding of common security practices for both mobile and web development. They should have experience with data encryption, secure storage, and authentication mechanisms.
12. IDEs
IDEs like IntelliJ IDEA and Android Studio support Kotlin. Using these tools increases productivity by offering features like code completion, refactoring, and debugging. This speeds up your app development project.
Soft skills to look for in your ideal Kotlin developer
13. Teamwork
A good Kotlin developer fits into team environments. Their role involves working closely with designers, backend engineers, product managers, and other professionals to build cohesive, high-performing applications. Look for a developer with strong interpersonal skills who can collaborate effectively. This includes active communication—both sharing ideas and listening to others.
14. Problem-solving
Great Kotlin developers are problem solvers. They should be able to navigate the complexity of mobile development, whether that’s handling asynchronous programming with coroutines or optimizing app performance. They should also troubleshoot issues, find innovative solutions, and continuously look for ways to improve the application.
15. Time management
Time management is crucial for Kotlin developers. They often need to juggle multiple tasks and deadlines to deliver projects on time. They should be able to prioritize tasks, manage project timelines, and produce high-quality results efficiently. Good time management keeps the development process on track, ensuring applications are delivered as scheduled.
16. Attention to detail
Kotlin development requires strong attention to detail. Developers should maintain high code quality and optimize app performance. They must debug meticulously, test thoroughly, and validate their work to create reliable applications that consistently enhance the user experience.
10 questions to identify top Kotlin developers
When interviewing Kotlin developers, ask questions that first assess the candidate’s technical skills and knowledge. Employers will usually conduct a coding test to test specific on-the-job knowledge.
The following set of questions will uncover not only the developer’s technical knowledge but also their problem-solving skills, teamwork, communication skills, and adaptability—all important skills for a collaborative environment.
Here are a few examples of technical interview questions:
1. How do you make sure your Kotlin code plays well with existing Java codebases?
Integration between Kotlin and Java is key to project continuity. I follow interoperability best practices by using Kotlin’s built-in support for calling Java code. I make sure Java classes and methods are correctly annotated for use in Kotlin and vice versa. I write tests to verify interoperability and maintain a consistent coding style for both languages.
2. How do you handle dependency injection in Kotlin applications?
Dependency injection (DI) is essential for building modular and testable code. In Kotlin applications, I use DI frameworks like Koin and Dagger-Hilt. Koin’s DSL is simple and integrates well with Kotlin, while Dagger-Hilt provides a compile-time verified approach. I configure these frameworks to inject dependencies where needed, so components remain loosely coupled and easy to test. This setup improves object creation, code maintainability, and scalability.
3. How do you test Kotlin applications?
I write unit tests using JUnit and MockK to mock dependencies and verify functionality. For Android-specific components, I use Espresso for UI testing and Robolectric for testing on the JVM. I also run integration tests to verify that different parts of the application work together correctly. Continuous integration tools like Jenkins or GitHub Actions help automate the testing process, providing immediate feedback on code changes.
4. How do you debug Kotlin code?
I use Android Studio’s built-in debugging tools like breakpoints, watches, and the debug console to inspect variables, analyze the call stack, and step through code. I also use logging with Logcat for quick checks and detailed inspections. Writing unit tests with JUnit and integration tests with Espresso helps catch errors early in the development lifecycle. I use tools like Firebase Crashlytics for runtime error monitoring in production, which tracks and analyzes crashes.
5. How do you make your Kotlin applications thread-safe?
To make Kotlin applications thread-safe, I use synchronization mechanisms to prevent concurrent access issues. I use synchronized blocks, Mutex from Kotlin coroutines, and atomic operations to manage shared resources. For complex scenarios, I rely on higher-level concurrency constructs like Channel and Flow in coroutines to handle concurrent data streams safely.
6. How do you manage dependencies in Kotlin projects?
I manage dependencies in Kotlin projects using build automation tools like Gradle. I define dependencies in the build.gradle.kts file for Kotlin DSL or the build.gradle file for Groovy DSL. I also use dependency management techniques like version catalogs, dependency locking, and custom configurations to maintain consistency across different modules and environments.
7. How do you learn new features or updates in Kotlin?
Since Kotlin and related technologies evolve quickly, developers need to stay current. This question helps assess how they keep up with the language and ecosystem.
8. What are the main differences between Kotlin and Java in your work?
Kotlin and Java are fully interoperable, but each has unique strengths. The candidate should explain how and when they use one over the other.
9. How do you work with other developers and team members on Kotlin projects?
Kotlin projects require teamwork. This question helps evaluate the candidate’s experience collaborating with others.
10. Can you explain a complex Kotlin concept to a non-technical stakeholder?
Developers need to communicate with both technical and non-technical stakeholders. This question helps assess the candidate’s ability to explain complex ideas clearly.
Frequently Asked Questions
What is Kotlin app development?
Kotlin app development involves building applications using the Kotlin language. While it's primarily used for Android development, it can also be applied to projects like cross-platform development with Kotlin Multiplatform.
Why should companies hire Kotlin developers?
Companies should hire Kotlin developers for Android, backend, cross-platform, web, and desktop app development. Kotlin is fully interoperable with Java and features a concise, expressive syntax that reduces code errors and improves productivity. Since Google officially supports Kotlin for Android development, it is a long-term viable option.
Is Kotlin used for mobile app development?
Yes, Kotlin is widely used for native Android app development. It is the recommended language for Android due to its interoperability with Java, modern features, and safety.
Can I hire remote Kotlin developers?
Yes, you can hire remote Kotlin developers. Many Kotlin developers work remotely, allowing you to tap into a global talent pool and access professionals with specialized skills.
How do I hire the best Kotlin developers?
To hire dedicated Kotlin developers, follow a thorough recruitment process:
- Define your requirements
- Use a mix of job boards, networking, and other recruitment channels
- Use automated systems (like ATS) to screen resumes
- Conduct technical interviews
- Review portfolios and referrals/testimonials
Are all Kotlin developers mobile app developers?
No, not all Kotlin developers build mobile apps. While Kotlin is commonly used for Android development, it is also used for backend, cross-platform, and web development.
How do Kotlin developers differ from Java developers?
Kotlin and Java are related programming languages, but Kotlin developers use modern features like concise syntax, null safety, and coroutines, which Java lacks. While both languages are interoperable, Kotlin is more commonly used for developing new, high-quality Android apps, whereas Java is often used for maintaining legacy Android projects.
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