About this role.
Ruby Labs is seeking a Senior Android Engineer to develop and maintain high-quality mobile apps. The role involves collaborating with cross-functional teams, implementing CI/CD pipelines, and ensuring top performance. Candidates need 5+ years of experience, expert Kotlin skills, and deep knowledge of modern Android architecture. Benefits include remote work, unlimited PTO, and a company-provided MacBook. This is a key position in a fast-growing tech company.
Role DNA
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Job Complexity
5/5Pace & Pressure
4/5Autonomy Level
4/5Communication Load
4/5Salary analysis
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Core skills
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Cover letter sample
Dear Hiring Manager,
I am excited to apply for the Senior Android Engineer position at Ruby Labs. With over 5 years of experience building high-quality B2C mobile apps, I have deep expertise in Kotlin, Jetpack Compose, and modern Android architecture. I have successfully implemented subscription billing using Google Play Billing Library and managed CI/CD pipelines with GitHub Actions.
My background includes optimizing app performance and leading cross-functional teams to deliver seamless user experiences. I am particularly drawn to Ruby Labs’ innovative portfolio and commitment to remote work flexibility.
I look forward to the opportunity to contribute to your team and drive the future of your consumer products. Thank you for your consideration.
Sincerely,
[Your Name]
Sample interview questions
I would use the BillingClient to query purchases and listen for purchase updates. For entitlement verification, I would implement a server-side validation using Real-time Developer Notifications (RTDN) and a webhook to handle subscription state changes. I would also cache entitlements locally and sync with the server to ensure consistency.
I use Compose's state management with remember, mutableStateOf, and StateFlow. For complex UI state, I often use a ViewModel with StateFlow or a sealed class to represent different states. I also leverage LaunchedEffect to handle side effects and collect flows safely.
I enforce coding standards through code reviews and static analysis tools like Detekt. I also write unit tests (JUnit, MockK) and UI tests (Compose UI testing). For multi-module, I use Gradle's module graph to manage dependencies and ensure each module has a clear responsibility.
I use Android Studio Profiler to identify memory leaks and jank. For startup time, I optimize by deferring non-critical initialization and using Baseline Profiles. I also analyze APK size with APK Analyzer and use App Startup library to initialize components efficiently.
I follow Android Developers Blog, Google I/O sessions, and community blogs. I also experiment with new libraries in side projects. When integrating, I evaluate the stability and benefits, then propose a phased adoption with thorough testing.
About us
Ruby Labs is a leading tech company that creates and operates innovative consumer products. We offer a diverse range of opportunities across the health, education, and entertainment industries. Our innovative teams are driving the future of consumer-led products, and we’re always looking for passionate individuals to join us. Learn more about our story at: https://rubylabs.com/about-us/
About the role
As a Senior Android Engineer, you will play a key role in developing and maintaining our mobile app, ensuring high performance, scalability, and a seamless user experience. You will collaborate closely with the product manager and fellow developers to bring new features to life and continuously optimize our app. Your expertise in Kotlin and Android development best practices will be instrumental in driving innovation and maintaining our position as a leader in the Play Store.
Key Responsibilities
Develop and maintain a high-quality Android application with a focus on performance, UI, and UX.
Take ownership of development processes, ensuring clean, maintainable, and scalable code.
Work with cross-functional teams to design, develop, and launch new features.
Implement CI/CD pipelines and deployment best practices.
Conduct code reviews and enforce coding standards.
Profile and optimize app performance (memory, jank, startup, battery, APK/AAB size).
Stay up to date with the latest Android development trends and integrate relevant advancements.
Qualifications
5+ years of professional Android development experience.
Experience with B2C mobile apps built on subscription business models.
Expert proficiency in Kotlin (coroutines, Flow, sealed classes, generics, extension functions).
Strong command of Google Play Billing Library v7+ and subscription lifecycle: purchase flows, entitlement management, Real-time Developer Notifications (RTDN), and server-side validation (with RevenueCat or a custom equivalent).
Deep understanding of Jetpack Compose and the Android View system, including interoperability and Compose state management (remember, State, StateFlow collection).
Strong grasp of modern Android architecture: MVVM/MVI, Clean Architecture, unidirectional data flow, and modularization (Gradle multi-module).
Proficiency with Jetpack libraries (ViewModel, Navigation, Room, WorkManager, DataStore) and Dependency Injection (Hilt/Dagger).
Experience with CI/CD (GitHub Actions, Bitrise, or Gitlab CI), Gitflow, and Play Console / internal-track distribution.
Automated testing experience: JUnit, Espresso, Compose UI testing, Turbine, and MockK.
Strong debugging and profiling skills with Android Studio Profiler, LeakCanary, and Baseline Profiles.
Experience integrating AI-driven features and/or AI-assisted development workflows.
Location
Ruby Labs operates within the CET (Central European Time) zone. Applicants from any country are welcome to apply for the position as long as they are located within approximately ± 4 hours of CET. This ensures optimal collaboration and communication during working hours.
Benefits
Discover the perks of being part of our vibrant team! We offer:
Remote Work Environment: Embrace the freedom to work from anywhere, anytime, promoting a healthy work-life balance.
Unlimited PTO: Enjoy unlimited paid time off to recharge and prioritize your well-being, without counting days.
Paid National Holidays: Celebrate and relax on national holidays with paid time off to unwind and recharge.
Company-provided MacBook: Experience seamless productivity with top-notch Apple MacBooks provided to all employees who need them.
Flexible Independent Contractor Agreement: Unlock the benefits of flexibility, autonomy, and entrepreneurial opportunities. Benefit from tax advantages, networking opportunities, reduced employment obligations, and the freedom to work from anywhere. Read more about it here: https://docs.google.com/document/d/1nkrN76JlZkbKj9WSOhlT1_mni_CZeDkHdwfIjPXVwvk/preview?tab=t.0#heading=h.ndsdl4wapxtt
Be part of our fast-growing team and seize this excellent opportunity for personal and professional growth!
Interview Process
After submitting your application, we conduct a thorough review which typically takes 3 to 5 days, but may occasionally take longer due to the volume of applications received. If we see a potential fit, we proceed with the following steps:
Recruiter Screening (40 minutes)
Technical Interview (90 minutes)
Technical Interview (60 minutes)
Final Interview (60 minutes)
Life at Ruby Labs
At Ruby Labs, we move fast, aim high, and expect the same from our team. We’re not here to play small—we’re here to build, grow, and win. That means we look for people who are ambitious, driven, and ready to give their best every single day.
This is a place for individuals who thrive under pressure, embrace challenges, and see opportunity in every obstacle. If you’re hungry to achieve, motivated by impact, and want to grow at the speed of your own ambition, Ruby Labs offers the platform to make it happen.
Here, effort is matched with reward. We recognize those who go all in and deliver results, and we create space for people who want more—more responsibility, more growth, and more success.
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