Kotlin Multiplatform Engineer (Senior-Staff Levels)

About Cantina: Cantina Labs is a social AI company, developing a suite of advanced real-time models that push the boundaries of expression, personality, and realism. We bring characters to life, transforming how people tell stories, connect, and create. We build and power ecosystems. Cantina, our flagship social AI platform, is just the beginning. If you're excited about the potential AI has to shape human creativity and social interactions, join us in building the future! About the Role: As a Kotlin Multiplatform Engineer at Cantina, you’ll be the architect of our shared-code strategy — building the foundation that powers our experiences across Android, iOS, and web from a single Kotlin codebase. You’ll work at the cutting edge of the KMP ecosystem, shipping production code to real users on multiple platforms, while keeping platform-specific layers feeling truly native. We’re looking for a Kotlin expert who has been in the trenches with KMP — someone who has wrestled with interop edge cases, navigated the wasm target, and shipped Compose Multiplatform UI that feels polished everywhere. What You'll Do: - Design and build shared KMP modules covering networking, data persistence, business logic, and domain models used across Android, iOS, and wasm targets. - Ship production-grade Compose Multiplatform UIs that feel native and performant on Android, iOS, and web. - Build optimized platform-specific targets — leveraging Swift/Obj-C interop for iOS and Kotlin/Wasm for web — to meet the performance and UX bar of each platform. - Architect clean platform-expect/actual boundaries and maintain Kotlin/Native and Kotlin/JS interop layers. - Set up and manage Koin Multiplatform for dependency injection across all targets, ensuring clean and testable module graphs. - Collaborate with platform teams (iOS, Android, web) to align on shared APIs, versioning, and release cadences. - Drive KMP best practices across the organization — tooling, testing strategies, CI/CD for multiplatform builds. - Lead development of new AI and media-driven features within the shared codebase. - Participate in architecture reviews and uphold high standards for shared module design and testability. What You'll Bring: - 8+ years of software engineering experience with deep, expert-level Kotlin — you know the language spec, not just the idioms. - Real-world, production KMP experience: you’ve shipped KMP code that real users ran on Android, iOS, and/or wasm — not just toy projects or internal tools. - Hands-on Compose Multiplatform experience: building shared UI across multiple targets with platform-specific adaptations. - Experience with Koin Multiplatform for dependency injection across KMP targets in production codebases. - Solid understanding of Kotlin/Native memory model, freezing, and interop with Obj-C/Swift APIs. - Experience targeting Kotlin/Wasm and/or Kotlin/JS, including the Compose for Web stack. - Fluency with multiplatform build tooling: Gradle multiplatform plugin, source sets, target configuration, and CI pipelines. - Strong grasp of coroutines, Flow, and structured concurrency — understanding how they behave across targets. - Ability to write readable, maintainable, thoroughly documented, and well-tested shared code. - Bonus: experience with KMP libraries (Ktor, SQLDelight) in production environments. - Bonus: contributions to the KMP/CMP open-source ecosystem or close familiarity with JetBrains’ roadmap. Compensation: The anticipated annual base salary range for this role is between $180,000-$230,000. When determining compensation, a number of factors will be considered, including skills, experience, job scope, location, and competitive compensation market data. Benefits: - Competitive salary and generous company equity - Medical, dental, and vision insurance – 99.99% of premiums covered by Cantina - 42 days of paid time off, including: - 15 PTO days - 10 sick days - 15 company holidays - 2 floating holidays - Generous parental leave & fertility sup