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The ultimate guide for hiring Kotlin developers
A preferred language for Android apps, Kotlin offers myriad features: concise syntax, enhanced safety features, and full interoperability with Java. With the rising demand for skilled Kotlin developers, comes the need to find the right talent for your projects.
We understand the intricacies of this selection process well. That’s because we have received over 2.2 million applications annually, and we've hired only the top 1% of LATAM tech professionals. Our extensive experience in recruiting top-tier developers has equipped us to create this comprehensive guide to simplify your hiring process, too.
Securing proficient Kotlin app developers is vital for your project's success and your company's growth. The process involves more than just assessing technical skills, however. It’s also about finding candidates who fit in with your team and can drive innovation within your company’s dynamics. This guide includes essential criteria, including key skills and practical interview questions with example answers. Our aim is to help you make better-informed hiring decisions and find the best-fit Kotlin developers for your team.
Before you start hiring
Culture fit
When hiring Kotlin developers, start by assessing how well they will fit into your company culture. To do that, you'll need to identify your organization's core values and assess 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 foster better teamwork and long-term collaboration. This will ultimately lead to more successful project outcomes.
Modernization
Consider your project's modernization needs and the role that a Kotlin developer will play in advancing your organization. Then, look for candidates who possess expertise in modern technologies and practices, such as reactive programming, microservices architecture, and cloud-native development. A developer who is skilled in updating legacy systems and integrating new solutions can help your organization stay competitive and innovative in a rapidly evolving tech landscape.
Collaborative mindset
Kotlin developers often need to work closely with other team members and key stakeholders. Look for candidates who have a demonstrated ability to collaborate in team settings and communicate with non-technical stakeholders. They should be able to articulate complex ideas clearly and work harmoniously with other developers, product managers, and other organizational members. A developer with a collaborative mindset will contribute to a more cohesive team environment.
Experience in your industry
Prioritize Kotlin developers who have experience in your specific industry. Industry-specific knowledge brings valuable insights and a deeper understanding of the challenges and any regulatory requirements that your organization faces on a day-to-day basis. A developer with relevant industry experience can 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 a key trait for Kotlin developers. This is especially true in the fast-paced and ever-changing nature of software development. Look for candidates who have demonstrated flexibility in learning new tools, frameworks, and methodologies. An adaptable developer can quickly adjust to changing project requirements, varying regulations, and new technological advancements. They should be able to handle the dynamic nature of Kotlin development and continue to contribute effectively to your team, regardless of the ebbs and flows.
16 skills every Kotlin developer should have
Kotlin is a modern, statically typed programming language. It has gained significant popularity for Android development in particular. That’s because of its concise syntax, enhanced safety features, and full interoperability with Java. These qualities make it an ideal choice for building high-performance applications and allow developers to write clearer and more maintainable code. The features ultimately reduce the likelihood of common programming errors. Read: Increased productivity. With features like coroutines for asynchronous programming and extensive support for functional programming paradigms, Kotlin offers a versatile toolkit for developing a wide range of applications.
A successful Kotlin developer combines strong technical skills with soft skills to drive project success. They should be proficient in Kotlin-specific frameworks, libraries, and development tools—and they should be able to build and maintain high-quality, scalable applications. However, soft skills are just as important for integrating seamlessly into team environments and driving innovation. By leveraging their technical expertise and interpersonal abilities, Kotlin developers can significantly enhance project outcomes.
Here are the hard and soft skills that Kotlin developers need to contribute to the overall growth and success of your organization.
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 within a Kotlin project, migrate projects from Java to Kotlin, and access Java libraries and frameworks.
2. Android app development
Because 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 enhances a Kotlin developer's capabilities. It allows them to leverage Kotlin features in backend frameworks like Ktor and Spring and facilitates more efficient development.
4. Object-oriented programming and functional programming
Understanding object-oriented and functional programming allows developers to fully tap into Kotlin's features. The multi-paradigm language supports both OOP and FP, and by choosing the right approach for the context, developers can develop more efficient and maintainable code.
5. Build tools and dependency management
Kotlin developers use build tools such as Gradle and Maven to automate project setup, compilation, and packaging. These tools help ensure consistency and reproducibility and ensure seamless integration with CI/CD pipelines.
6. Version control
Version control systems like Git facilitate stronger collaboration, change tracking, branching and merging, code backup, and continuous integration. These are crucial practices for managing 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 for improving code quality, speeding up deployment, and ensuring consistency.
9. Database management
Kotlin developers should be proficient in database management to ensure offline access, scalability, data security, and offline access. They should have knowledge of SQL and experience with relationship databases like SQLite and PostgreSQL.
10. Networking
Experience with HTTP, REST, WebSocket, Retrofit, and Ktor helps enable data exchange, enhance functionality, and improve the 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 offer Kotlin support. Using these tools enhances productivity by offering features such as code completion, refactoring, and debugging. This streamlines and accelerates your app development project.
Soft skills to look for in your ideal Kotlin developer
13. Teamwork
An effective Kotlin developer thrives in collaborative settings. Their role tends to involve working closely with designers, backend engineers, product managers, and other professionals to build cohesive, high-performing applications. Look for a developer who possesses strong interpersonal skills and can work seamlessly with others on your team. This includes active communication—which means both sharing their ideas and listening to others.
14. Problem-solving
Great Kotlin developers are also adept problem solvers. They should be able to easily navigate the intricacies of mobile development, whether that’s handling asynchronous programming with coroutines or optimizing app performance. They should also demonstrate the ability to troubleshoot issues, find innovative solutions, and look for ways to continuously improve the application.
15. Time management
Time management is crucial for Kotlin developers. They often need to juggle multiple tasks and deadlines to ensure projects are completed on time. They must also be capable of prioritizing tasks, managing project timelines, and delivering high-quality results efficiently. Good time-management skills ensure that the development process runs as smoothly as possible so that applications are delivered on schedule.
16. Attention to detail
Kotlin development demands a keen attention to detail. Developers should be able to ensure high code quality and optimized app performance. They should meticulously debug code, conduct thorough testing, and validate their work to achieve reliable applications that continuously improve the user experience.
10 questions to identify top Kotlin developers
When interviewing Kotlin developers, it's important to ask questions that first assess the candidates' technical skills and knowledge. Employers will also usually conduct a coding test to further assess specific on-the-job knowledge.
The following set of questions aims to uncover not only the developer's technical knowledge but also their problem-solving abilities, teamwork, communication skills, and adaptability—all crucial traits for success in a collaborative environment.
Here are a few examples of technical interview questions:
1. How do you ensure your Kotlin code integrates well with existing Java codebases?
Ensuring seamless integration between Kotlin and Java is crucial for maintaining project continuity. I follow interoperability best practices by using Kotlin's built-in support for calling Java code. I make sure that Java classes and methods are correctly annotated for use in Kotlin and vice versa. I also write tests to verify the interoperability and maintain a consistent coding style across both languages.
2. How do you handle dependency injection in Kotlin applications?
Dependency injection (DI) is essential for creating modular and testable code. In Kotlin applications, I use DI frameworks like Koin and Dagger-Hilt. Koin's DSL is straightforward and integrates well with Kotlin. On the other hand, Dagger-Hilt provides a compile-time verified approach. I configure these frameworks to inject dependencies where needed, making sure that components are loosely coupled and easy to test. This setup helps me efficiently manage object creation, improve code maintainability, and increase scalability.
3. What is your approach to testing Kotlin applications?
I write unit tests using JUnit and MockK to mock dependencies and verify functionality. For Android-specific components, in particular, I use Espresso for UI testing and Robolectric for running tests on the JVM. I also employ integration tests to ensure different parts of the application work together correctly. Continuous integration tools like Jenkins or GitHub Actions allow me to automate the testing process with immediate feedback on code changes, as well.
4. What is your approach to debugging 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 allows me to catch errors as early on in the development lifecycle as possible. But for runtime error monitoring in production, I use tools like Firebase Crashlytics, which tracks and analyzes any crashes.
5. How do you ensure thread safety in Kotlin applications?
To ensure thread safety in Kotlin applications, I use synchronization mechanisms to prevent concurrent access issues. I leverage tools like synchronized blocks, Mutex from Kotlin coroutines, and atomic operations to safely manage shared resources. For complex scenarios, I leverage higher-level concurrency constructs like Channel and Flow in coroutines. I do this to handle concurrent data streams in a thread-safe manner.
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. I use these to ensure consistent and maintainable dependency management across different modules and environments.
7. How do you approach learning new features or updates in Kotlin?
Since Kotlin and related technologies are constantly evolving, it's important to understand how developers stay up to date with the language and ecosystem.
8. What are some differences between Kotlin and Java that you find significant in your work?
Kotlin and Java are related and fully interoperable. The candidate should be able to explain how and when they use one language over the other.
9. How do you collaborate with other developers and team members when working on Kotlin projects?
Kotlin projects often require teamwork. This question will help you evaluate the candidate's experience collaborating with team members.
10. Can you describe a time when you had to explain a complex Kotlin concept to a non-technical stakeholder?
It's important for developers to communicate with both technical and non-technical stakeholders. This helps you assess the candidate's communication skills.
FAQ
What is Kotlin app development?
Kotlin app development involves building applications with the Kotlin language. The programming language is frequently used for Android app development and can be applied to other projects, such as cross-platform development through Kotlin Multiplatform.
Why should companies hire Kotlin developers?
You should hire a Kotlin developer for Android, backend, cross-platform, web, and desktop app development. The language is fully interoperable with Java and offers concise and expressive syntax. This reduces code errors and improves productivity. Kotlin is also officially supported by Google for Android app development, which ensures its long-term viability.
Is Kotlin used for mobile app development?
Yes, Kotlin is used for native Android app development. It's the preferred language for Android because of its interoperability with Java, modern features, and enhanced safety.
Can I hire remote Kotlin developers?
Yes, you can hire remote Kotlin developers. Kotlin developers frequently work remotely. By using this model, you can 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, you should follow a thorough recruitment process:
- Define your requirements.
- Use a mix of job boards, networking, and other recruitment vehicles.
- Use automated systems (such as ATS) to screen resumes.
- Conduct technical interviews.
- Review portfolios and referrals/testimonials.
Are all Kotlin developers mobile app developers?
No, not all Kotlin developers focus on building mobile apps. While Kotlin is frequently used for Android app development, it can also be applied to backend development, cross-platform development, and web development.
How do Kotlin developers differ from Java developers?
Kotlin and Java are related programming languages, but Kotlin and Java developers are not identical. Kotlin developers leverage the newer language's modern features, including concise syntax, null safety, and coroutines. These features are not available in Java. Moreover, while the languages are interoperable, Kotlin is more frequently used to create new, high-quality mobile apps for Android. Java, meanwhile, is largely used for legacy Android projects.
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