Kotlin Multiplatform Developer

🏢 Summary: The role focuses on architecting and maintaining shared business logic and high-performance networking/data layers using Kotlin Multiplatform for Android and iOS. You will own the shared codebase, ensure production-grade quality through robust testing, and align mobile and backend systems. The position emphasizes API strategy, CI/CD integration, and technical leadership in multiplatform development. 🗂️ Requirements: Proven experience with Kotlin Multiplatform for shared logic and networking layers, Strong knowledge of RESTful API communication and contract testing, Experience with serialization and secure authentication flows, Hands-on experience with multiplatform testing frameworks, Ability to collaborate with backend engineers on APIs and schemas, Minimum 5 years of commercial software development experience 📃 Skills: Kotlin, KotlinMultiplatform, KMP, REST, APIs, Serialization, KotlinX, Authentication, CI/CD, Testing, Android, iOS 🏢 Description: The Role As a key contributor to our cross-platform strategy, you will architect and refine shared business logic using Kotlin Multiplatform (KMP) . Your primary focus will be on engineering high-performance networking and data layers that serve both Android and iOS ecosystems. You won't just write code—you will take full ownership of the shared codebase, ensuring it remains scalable, maintainable, and robust in production. Operating at the heart of our mobile-to-backend infrastructure, you will drive technical excellence and help shape the future of our multiplatform development standards. Key Responsibilities Cross-Platform Engineering: Design and implement core business logic and data flows using Kotlin Multiplatform to ensure seamless performance across mobile platforms. API Strategy & Alignment: Partner with backend teams to define and validate API contracts. You will oversee serialization, secure authentication flows, versioning, and sophisticated error-handling strategies. Quality & Testing Excellence: Build and maintain comprehensive integration and E2E testing suites specifically for KMP, ensuring the shared layer is stable and reliable. Bridge Backend & Mobile: Act as a technical liaison to ensure that backend behavior perfectly aligns with mobile client requirements and user expectations. CI/CD Integration: Streamline test execution within CI pipelines to achieve high coverage and deterministic results for all shared mobile components. Requirements KMP Expertise: Proven track record in building shared logic, networking layers, and data persistence using Kotlin Multiplatform. Backend Savvy: Deep understanding of RESTful/API communication, including retry logic, serialization (e.g., KotlinX Serialization), and contract testing. Testing Rigor: Hands-on experience with multiplatform testing frameworks to dliver high-quality, production-ready code. Collaboration Skills: Ability to work effectively with backend engineers on complex schemas, auth flows, and system consistency. Professional Experience: A minimum of 5 years of commercial software development experience.

🏢 Summary: The offer is for a Kotlin Multiplatform Engineer to build secure cross-platform mobile modules within a Zero Trust Architecture initiative. The role focuses on implementing secure authentication, identity management, and runtime protection in mobile applications using KMM. You will collaborate with security teams to deliver scalable and security-driven mobile solutions. 🗂️ Requirements: Strong experience with Kotlin, Experience in mobile development (Android or cross-platform), Hands-on experience with Kotlin Multiplatform Mobile (KMM), Understanding of OAuth 2.0 and OpenID Connect, Experience with identity providers and token management, Knowledge of mobile security best practices, Experience implementing Zero Trust Architecture principles, Familiarity with secure storage on mobile platforms 📃 Skills: Kotlin, KMM, Android, OAuth2, OpenIDConnect, MFA, SSO, ZeroTrust, Security, IdentityProviders, SecureStorage 🏢 Description: Tech stack: Kotlin Multiplatform (KMM) Kotlin and mobile development (Android or cross-platform) OAuth 2.0, OpenID Connect Requirements: Strong experience with Kotlin and mobile development (Android or cross-platform) Hands-on experience with Kotlin Multiplatform Mobile (KMM) Solid understanding of authentication and authorization protocols (OAuth 2.0, OpenID Connect) Experience working with identity providers and secure session/token management Good understanding of mobile security best practices Experience implementing or working with Zero Trust Architecture principles Familiarity with secure storage solutions on mobile platforms Strong problem-solving skills and attention to detail Good command of English (B2+) Nice to have: Experienced in using AI tools in day-to-day workflow Experience with mobile security frameworks or SDKs Knowledge of device security signals and threat detection mechanisms Background in cybersecurity or working with security teams Experience in enterprise-scale environments Project description: We are looking for a Kotlin Multiplatform Engineer to join a security-focused initiative within a large international organization. The project is centered around implementing Zero Trust Architecture principles in mobile applications, with a strong emphasis on secure authentication, identity management, and runtime protection. You will work closely with security architects and cross-functional teams to build secure, scalable, and high-quality mobile solutions. Main responsibilities: Develop and maintain cross-platform modules using Kotlin Multiplatform Mobile (KMM) Design and implement secure authentication and authorization flows (OAuth 2.0, OpenID Connect, MFA, SSO) Integrate with identity providers and enforce Zero Trust principles (least privilege, continuous verification) Collaborate with security architects to embed security best practices into mobile client design Ensure secure storage of credentials and tokens using platform-specific secure storage mechanisms Monitor and respond to runtime security signals (e.g., device integrity, jailbreak/root detection) Write clean, maintainable, and testable Kotlin code for both shared and platform-specific modules

🏢 Summary: Senior Kotlin Multiplatform Developer role focused on building cross-platform applications with shared business logic for Android and iOS. The position involves contributing to architecture, integrating mobile solutions, and maintaining technical standards in a hybrid B2B setup. 🗂️ Requirements: 5+ years of software development experience, 2+ years of commercial Kotlin experience, 1+ year of hands-on Kotlin Multiplatform experience, Experience delivering at least one production-grade multiplatform application, Strong knowledge of Kotlin, Strong knowledge of Coroutines and Flow, Experience with Kotlin Multiplatform, Experience with Android development using Jetpack Compose, ViewModel, Hilt or Koin, Experience with iOS integration using Swift or SwiftUI, Knowledge of Clean Architecture and MVVM or MVI, Experience with REST APIs and GraphQL, Experience with unit and integration testing, Knowledge of Gradle and CI/CD pipelines 📃 Skills: Kotlin, KMP, Coroutines, Flow, Android, Jetpack, Compose, ViewModel, Hilt, Koin, Swift, SwiftUI, MVVM, MVI, REST, GraphQL, Gradle, CI/CD, GitHub, GitLab, Testing 🏢 Description: Kotlin Multiplatform Developer (KMP) Location: Warsaw, Poland (Hybrid – 4 days per month in the office) Contract: B2B via Experis Start Date: ASAP / up to 30 days notice About the Role We are looking for a Senior Kotlin Multiplatform Developer to design and deliver modern cross-platform applications. You will be responsible for building shared business logic and data layers, integrating solutions across Android and iOS, and contributing to architecture and technical standards. Requirements - 5+ years of software development experience - 2+ years of commercial Kotlin experience - 1+ year of hands-on Kotlin Multiplatform (KMP) experience - Experience delivering at least one production-grade multiplatform application - Strong knowledge of: - Kotlin, Coroutines, Flow - Kotlin Multiplatform (KMP) - Android (Jetpack Compose, ViewModel, Hilt/Koin) - iOS integration with Swift/SwiftUI - Clean Architecture, MVVM/MVI - REST APIs, GraphQL - Unit and integration testing - Gradle and CI/CD (GitHub Actions or GitLab CI) Nice to Have - Compose Multiplatform - Ktor - Kotlin/JS or WebAssembly - Advanced CI/CD knowledge - Domain-Driven Design (DDD) What We Offer - Long-term B2B cooperation via Experis - Hybrid work model (4 days/month from Warsaw office) - Medicover private healthcare - Multisport card - Group life insurance - Access to e-learning platforms

🏢 Summary: Opportunity to lead the development of a cross-platform mobile app built with Kotlin Multiplatform for Android and iOS, taking full ownership of architecture, shared components, and UI/UX patterns. The role involves close collaboration with backend and design teams to deliver scalable, high-performance mobile experiences. You will shape the technical foundations of the product as part of the founding engineering team. 🗂️ Requirements: 4+ years of Android development experience, Strong proficiency in Kotlin, Production experience with Jetpack Compose, Hands-on experience with Kotlin Multiplatform, Experience with mobile architecture patterns (MVI or MVVM), Experience designing mobile app architecture, Experience integrating mobile apps with backend APIs 📃 Skills: Kotlin, Android, iOS, Jetpack, Compose, KotlinMultiplatform, MVI, MVVM, REST, API 🏢 Description: About the company We are a new AI startup, recently funded, creating the next generation of digital experiences for collectibles and trading cards, like game cards, sports cards, and more. The company was started by two experienced entrepreneurs who have built and grown successful companies before, including a gaming unicorn. We are now forming our founding engineering team. This team will help shape the product, company culture, and engineering standards. We use modern tools, LLM-assisted development, automation, and fast iteration. We are looking for smart and motivated engineers who enjoy working with less guidance, more ownership, and some uncertainty. Most of our work happens on-site. About the role You will take full responsibility for our mobile app, built with Kotlin Multiplatform for both Android and iOS. You will help design the app’s architecture, set UI/UX patterns, and work closely with backend and design teams. What you’ll do Build the main app in Kotlin Multiplatform for Android and iOS Set up clean architecture patterns and shared components across platforms Work with backend to create mobile-friendly APIs and data structures Collaborate with design to make smooth, polished, and fast user experiences Who you are 4+ years of Android development experience, strong in Kotlin Experience with Jetpack Compose in production or serious side projects Experience with Kotlin Multiplatform Comfortable with client architecture patterns (MVI, MVVM, etc.) Take ownership and have a good product sense Enjoy creating UI experiences with care, speed, and quality What it’s like to work here High ownership, low bureaucracy Chance to shape company culture and the codebase from the start Work directly with founders and product team Competitive salary and meaningful equity Fast-paced environment, no silos, no drama

🏢 Summary: Development role focused on building secure cross-platform mobile solutions using Kotlin Multiplatform Mobile aligned with Zero Trust Architecture principles. The position involves implementing strong authentication and authorization mechanisms, integrating with enterprise identity providers, and ensuring secure credential storage and runtime protection on Android and iOS. 🗂️ Requirements: Strong experience with Kotlin development, Hands-on experience with Kotlin Multiplatform Mobile (KMM), Knowledge of OAuth 2.0 and OpenID Connect, Experience implementing MFA and SSO, Experience integrating mobile apps with IAM or Identity Providers, Knowledge of secure token handling and credential storage on Android and iOS, Ability to write automated tests, Understanding of mobile security risks and mitigation techniques 📃 Skills: Kotlin, KMM, OAuth2, OpenIDConnect, MFA, SSO, IAM, Android, iOS, Keystore, Keychain, ZeroTrust 🏢 Description: Kotlin Multiplatform Developer (KMM) – Zero Trust Architecture (m/f/d) Role Overview We are looking for a Kotlin Multiplatform Developer to join a team building secure mobile solutions aligned with Zero Trust Architecture principles. The role involves developing and maintaining shared cross-platform modules using Kotlin Multiplatform Mobile (KMM) , implementing secure authentication and authorization mechanisms, and integrating with enterprise identity providers. Key Responsibilities Develop and maintain cross-platform modules using Kotlin Multiplatform Mobile (KMM) . Implement secure authentication and authorization flows such as OAuth 2.0 , OpenID Connect , MFA , and SSO . Integrate with identity providers and enforce least privilege access and continuous verification . Collaborate with security architects to embed Zero Trust principles into mobile client design. Ensure secure storage of credentials and tokens using platform-specific mechanisms (e.g., Android Keystore , iOS Keychain ). Monitor and respond to runtime security signals (e.g., device integrity checks, jailbreak/root detection). Write clean, testable, and efficient Kotlin code for both shared and platform-specific modules. Requirements Strong experience with Kotlin development. Hands-on experience with Kotlin Multiplatform Mobile (KMM) . Good understanding of security standards and protocols: OAuth 2.0 , OpenID Connect , MFA, SSO. Experience integrating mobile apps with IAM / Identity Providers . Knowledge of secure token handling and credential storage on Android/iOS. Ability to write maintainable code and automated tests. Understanding of mobile security risks and mitigation techniques. Nice to Have Experience working in environments applying Zero Trust Architecture . Familiarity with mobile device integrity solutions and anti-tampering approaches. Experience in regulated industries (banking, fintech, enterprise security).

🏢 Summary: Senior Mobile Engineer role focused on designing and delivering high-quality, scalable mobile applications for both iOS and Android in an international project. The position involves contributing to architecture decisions, ensuring performance and security, and maintaining code quality through best practices and testing. 🗂️ Requirements: 7+ years of mobile development experience, Strong experience with iOS development using Swift, Strong experience with Android development using Kotlin, Solid understanding of MVVM or Clean Architecture, Experience integrating RESTful APIs, Knowledge of mobile performance, scalability, and security best practices, Experience working with Agile methodologies (Scrum or Kanban) 📃 Skills: Swift, Kotlin, iOS, Android, MVVM, CleanArchitecture, REST, Performance, Scalability, Security, Agile, Scrum, Kanban 🏢 Description: We are looking for a Senior Mobile Engineer with strong experience in both iOS (Swift) and Android (Kotlin) to join an international project focused on building high-quality mobile applications. Main Responsibilities: Design, develop, and maintain mobile applications for both iOS and Android platforms Contribute to the architecture and technical decisions of mobile solutions Build scalable, high-performance, and user-focused applications Collaborate closely with Product Managers, Designers, and other Engineers Ensure code quality through best practices, code reviews, and testing Troubleshoot, debug, and optimize application performance Key Requirements: 7+ years of experience in mobile development Strong hands-on experience with: iOS (Swift) Android (Kotlin) Solid understanding of mobile architectures (e.g., MVVM, Clean Architecture) Experience integrating RESTful APIs Knowledge of mobile performance, scalability, and security best practices Experience with Agile methodologies (Scrum/Kanban) Strong problem-solving skills and attention to detail Good communication skills in English Nice to Have: Experience with cross-platform solutions (e.g., Kotlin Multiplatform, Flutter, React Native) Familiarity with CI/CD pipelines for mobile applications Experience with automated testing (unit/UI) Knowledge of mobile app distribution processes (App Store / Google Play)

🏢 Summary: Senior/Lead Mobile Developer role focused on leading the design and development of advanced iOS and Android applications using Swift and Kotlin. The position involves architecting scalable mobile solutions, ensuring high code quality, and driving best practices across the development lifecycle. You will also provide technical leadership while delivering secure, high-performance mobile applications. 🗂️ Requirements: 3+ years experience with Swift for iOS development, 3+ years experience with Kotlin for Android development, Experience leading or mentoring development teams, Experience with RESTful APIs and backend integration, Experience with third-party libraries, Experience with CI/CD pipelines, Experience with automated testing, Experience with deployment processes, Knowledge of mobile architecture best practices, Experience with performance optimization and debugging, Knowledge of mobile security best practices 📃 Skills: Swift, Kotlin, iOS, Android, REST, CICD, APIs, AutomatedTesting, Deployment, Architecture, Security, Libraries, Backend 🏢 Description: We are looking for a highly skilled Senior/Lead Mobile Developer with deep expertise in Swift/Kotlin to join our mobile development team. In this role, you will lead the design, development, and optimization of cutting-edge applications, ensuring best practices in architecture, code quality, and user experience. You will mentor junior developers, collaborate with cross-functional teams, and play a key role in shaping our mobile strategy. Responsibilities Lead the design, development, and deployment of advanced iOS and Android applications using Swift and/or Kotlin Architect robust, scalable, and maintainable codebases, ensuring adherence to best practices and coding standards Collaborate with product managers, designers, and backend engineers to deliver seamless user experiences Mentor and guide junior developers, conducting code reviews and providing technical leadership Stay up-to-date with the latest iOS/Android trends, technologies, and best practices Troubleshoot, debug, and optimize application performance Ensure the security and privacy of user data in compliance with industry standards Requirements Extensive experience developing iOS applications with Swift (3+ years) Extensive experience developing Android applications with Kotlin (3+ years) Proven track record of leading or mentoring development teams Experience with RESTful APIs, third-party libraries, and integration of backend services Familiarity with CI/CD pipelines, automated testing, and deployment processes Good work ethic and strong sense of ownership of the end result Excellent verbal and written communication skills, B2 level of English We offer/Benefits We gather like-minded people: Engineering community of industry professionals Friendly team and enjoyable working environment Flexible schedule and opportunity to work remotely within Poland Chance to work abroad for up to 60 days annually Business-driven relocation opportunities We provide growth opportunities: Outstanding career roadmap Leadership development, career advising, soft skills, and well-being programs Certification (GCP, Azure, AWS) Unlimited access to LinkedIn Learning, Get Abstract, Cloud Guru English classes We cover it all: Stable income (Employment Contract or B2B) Participation in the Employee Stock Purchase Plan Benefits package (health insurance, multisport, shopping vouchers) Strategically located offices featuring entertainment and relaxation zones, table tennis and football, free snacks, fantastic coffee, and more Referral bonuses Corporate, social and well-being events Please, note: The set of bonuses might vary based on the role you apply for – specifics will be discussed with our recruiter during the general interview. We will reach out to selected candidates exclusively. EPAM is a leading global provider of digital platform engineering and development services. We are committed to having a positive impact on our customers, our employees, and our communities. We embrace a dynamic and inclusive culture. Here you will collaborate with multi-national teams, contribute to a myriad of innovative projects that deliver the most creative and cutting-edge solutions, and have an opportunity to continuously learn and grow. No matter where you are located, you will join a dedicated, creative, and diverse community that will help you discover your fullest potential.

🏢 Summary: Senior Android Engineer role focused on building and maintaining a large-scale mobile product using Kotlin and Jetpack Compose, with strong ownership of architecture, scalability, and code quality. The position involves working within a mature Android ecosystem, ensuring high performance and robust engineering standards. Candidates are expected to contribute autonomously to mobile architecture and delivery processes. 🗂️ Requirements: Strong Kotlin proficiency, Experience with Jetpack Compose, Deep knowledge of Android SDK, Understanding of OOP principles, Knowledge of algorithms, Knowledge of data structures, Experience with Gradle build systems, Experience with CI pipelines, Ability to work autonomously, Strong problem-solving skills 📃 Skills: Kotlin, Compose, Android, AndroidSDK, OOP, Algorithms, DataStructures, Gradle, CI, KMM, TDD, Copilot, PairProgramming, ModularArchitecture 🏢 Description: Senior Android Engineer (Kotlin / Compose) We are looking for an experienced Android Engineer who thrives in large-scale product environments and takes ownership of mobile architecture and delivery quality. You’ll work on a mature mobile ecosystem where scalability, performance, and engineering standards matter. What We’re Looking For Strong proficiency in Kotlin and modern Jetpack Compose for UI development Deep understanding of the Android SDK and native mobile development principles Solid knowledge of Object-Oriented Programming , algorithms, and data structures Experience working with Gradle-based build systems and CI pipelines Ability to work with a high level of autonomy and strong problem-solving mindset Additionally Valued Experience with modular architecture (e.g., Kotlin Multiplatform Mobile – KMM) Experience working within large and evolving codebases Practical exposure to Test-Driven Development (TDD) and Pair Programming Experience leveraging AI-assisted development tools (e.g., Copilot)

🏢 Summary: Development and large-scale delivery of Android applications for B2B and B2C clients, with responsibility for architecture, quality, and production maintenance. The role involves designing mobile-to-backend integrations, applying modern architectural patterns, and supporting CI/CD and monitoring processes. You will contribute to feature scoping, performance optimization, and continuous improvement of Android solutions. 🗂️ Requirements: Minimum 4 years commercial experience in Android development, Degree in Computer Science, Software Engineering or related field, Strong knowledge of software engineering principles, testing, data structures and algorithms, Hands-on experience designing mobile and backend architectures, Experience with MVI and TCA architectural patterns, Experience with REST or GraphQL APIs, Strong experience with CI/CD processes, Knowledge of OOP, SOLID principles and Clean Code, Experience with dependency injection and multithreading, Experience working in Agile methodologies (SCRUM or Kanban) 📃 Skills: Kotlin, Android, REST, GraphQL, CI/CD, MVI, TCA, OOP, SOLID, CleanCode, DependencyInjection, Threading, Scrum, Kanban, DataStructures, Algorithms 🏢 Description: About the role We are seeking candidates for our client, which operates in Europe. You will be a member of a team responsible for the development and delivery of mobile Android apps. A strong hands-on experience in delivering Android apps to customers on a large scale, supported with CI/CD processes and production monitoring, is a requirement. Technologies we work with: Kotlin, Android, AWS, Typescript, JavaScript, Node.js, REST/GraphQL APIs. Responsibilities Development and delivery of Android apps for B2B and B2C clients Design software architecture between mobile apps and systems that they connect with Follow and improve the concepts of dependency injection and threading inside apps Scoping and assessing the complexity of features Continuously improve the quality and performance of mobile apps Maintaining apps on production used by consumers from several European countries Monitor and create prototypes for new technological opportunities (E.g., WearOS) Participating in sprint planning, daily sprints and meetings with product owners for grooming new features Recruiting new team members Collaborating with other team members and teams that depend on the functionalities that you develop Required qualifications Minimum of 4 years commercial work experience in building Android apps Bachelor's or higher degree in Computer Science, Software Engineering, or a related field Strong understanding of software engineering principles, testing, data structures and algorithms Solid hands-on experience in solving architectural problems for mobile apps and backend services Fluency in architecture and patterns: MVI, TCA, REST/GraphQL APIs Strong hands-on experience of CI&CD processes Understanding of OO design patterns, dependency injection, SOLID principles and Clean Code Able to work with Agile methodologies such as SCRUM and/or Kanban Good communication and collaboration skills Team player and a leading by example approach Self-motivation, proactive attitude Proficiency in English, it’s our daily business language Nice to have Experience in developing Cloud and Infrastructure solutions with AWS and CI/CD processes supported by tools like Docker, Kubernetes, Jenkins, Terraform, CircleCI, GitlabCI, Datadog, etc. Working experience with one of the object-oriented and/or functional languages such as Elixir, C++, C#, Golang, Erlang, Python, Kotlin, Node.js

🏢 Summary: The role involves developing and delivering large-scale Android applications for B2B and B2C clients across Europe, with full ownership from architecture design to production support. The position focuses on building high-quality mobile solutions integrated with backend systems and supported by CI/CD and monitoring processes. You will work on improving app performance, architecture, and scalability within an Agile environment. 🗂️ Requirements: Minimum 3 years commercial experience in Android development, Bachelor’s degree in Computer Science, Software Engineering or related field, Experience delivering Android apps at scale, Strong knowledge of software engineering principles, data structures and algorithms, Hands-on experience designing mobile and backend architecture, Experience with TCA architecture, Knowledge of MVI architecture, Experience with REST APIs, Hands-on experience with CI/CD processes, Understanding of OOP, SOLID and Clean Code principles, Experience with dependency injection and threading in Android, Experience working in Agile (SCRUM or Kanban), English proficiency 📃 Skills: Kotlin, Android, AWS, TypeScript, JavaScript, Node.js, REST, TCA, MVI, CI/CD, OOP, SOLID, CleanCode, SCRUM, Kanban 🏢 Description: About the role We are seeking candidates for our client, which operates in Europe. You will be a member of a team responsible for the development and delivery of mobile Android apps. Hands-on experience in delivering Android apps to customers on a large scale, supported with CI/CD processes and production monitoring, is a requirement. Technologies we work with: Kotlin, Android, AWS, Typescript, JavaScript, Node.js, REST APIs. Responsibilities: Development and delivery of Android apps for B2B and B2C clients Design software architecture between mobile apps and systems that they connect with Follow and improve the concepts of dependency injection and threading inside apps Scoping and assessing the complexity of features Continuously improve the quality and performance of mobile apps Maintaining apps on production used by consumers from several European countries Monitor and create prototypes for new technological opportunities (E.g., WearOS) Participating in sprint planning, daily sprints and meetings with product owners for grooming new features Collaborating with other team members and teams that depend on the functionalities that you develop Required qualifications: Minimum of 3 years commercial work experience in building Android apps Bachelor's or higher degree in Computer Science, Software Engineering, or a related field Strong understanding of software engineering principles, testing, data structures and algorithms Solid hands-on experience in solving architectural problems for mobile apps and backend services Experience with TCA architecture Fluency in other architecture and patterns: MVI, REST APIs Strong hands-on experience of CI&CD processes Understanding of OO design patterns, dependency injection, SOLID principles and Clean Code Able to work with Agile methodologies such as SCRUM and/or Kanban Good communication and collaboration skills Team player Self-motivation, proactive attitude Proficiency in English, it’s our daily business language Nice to have: Experience in developing Cloud and Infrastructure solutions with AWS and CI/CD processes supported by tools like Docker, Kubernetes, Jenkins, Terraform, CircleCI, GitlabCI, Datadog, etc. Working experience with one of the object-oriented and/or functional languages such as Elixir, C++, C#, Golang, Erlang, Python, Kotlin, Node.js