About this role.
Ruby Labs is seeking a Senior React Native Developer to lead mobile expansion and shape the future of consumer products across health, education, and entertainment. The role involves building and scaling mobile apps, defining architecture, mentoring engineers, and ensuring high performance and reliability. Candidates should have 5+ years of mobile experience with significant React Native expertise, a strong understanding of mobile system design, and experience with CI/CD and app store deployments. This is a remote position requiring alignment with CET timezone, offering unlimited PTO and a flexible work environment. The ideal candidate is passionate about product quality and takes ownership of real features that users rely on.
Role DNA
A quick view of the complexity, pace, ownership and collaboration implied by the job description.
Job Complexity
4/5Pace & Pressure
3/5Autonomy Level
5/5Communication Load
5/5Salary analysis
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Core skills
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Cover letter sample
Dear Hiring Team,
I am writing to express my strong interest in the Senior React Native Developer position at Ruby Labs. With over 5 years of experience building and scaling mobile applications using React Native, I have a proven track record of delivering high-quality, performant apps that users love. I am particularly drawn to Ruby Labs' innovative consumer products and the opportunity to lead mobile architecture and mentor a growing engineering team.
In my previous role, I successfully led the migration of a legacy mobile app to a modern React Native architecture, reducing crash rates by 40% and improving startup time by 30%. I am skilled in state management, native module bridging, CI/CD, and performance optimization. I thrive in ownership-driven environments and am excited about the chance to shape the mobile strategy at Ruby Labs.
I look forward to the possibility of contributing to your team and helping deliver seamless mobile experiences. Thank you for considering my application.
Sincerely,
[Your Name]
Sample interview questions
In a previous project, the app had significant UI jank and slow navigation transitions. I used React Native's built-in Profiler and Flipper to identify expensive re-renders and memory leaks. I optimized by implementing React.memo, useMemo, and useCallback, lazy loading screens, and using FlatList with getItemLayout for large lists. I also moved heavy computations to native modules. Result: navigation became smooth, and frame rate improved from 30fps to 60fps.
I would first review the changelog and breaking changes. Then, create a new branch and update dependencies incrementally, testing each step. I'd use a tool like React Native Upgrade Helper to see diffs. Key steps: update native project files, fix deprecations, run the app on both iOS and Android, and fix any build errors. Post-upgrade, run regression tests and performance benchmarks. I'd also consider using a CI pipeline to automate testing.
State management libraries manage global app state, reducing prop drilling and providing predictable state updates. Redux is great for complex apps with many global states, middleware, and devtools, but has boilerplate. Zustand is simpler, smaller, and easier to learn for smaller to medium apps. I'd choose Redux if the app needs strict structure, undo/redo, or extensive middleware (e.g., sagas). For a lighter app with simple state, Zustand or even React Context would suffice.
First, I would design the data layer to cache recent data locally using AsyncStorage or SQLite. For network requests, I'd use a library like Redux Offline or Apollo Client with offline persistence. I'd implement a sync strategy: optimistic updates for user actions, queue failed requests, and sync when connection is restored. I'd also show UI indicators (e.g., offline banner) and handle conflict resolution. Key libraries: NetInfo for connectivity, Redux Persist for caching state, and a queue system for mutations.
I enforce coding standards with ESLint and Prettier, and use TypeScript for type safety. Code reviews are mandatory, and I advocate for SOLID principles and component reusability. I write unit tests with Jest and React Native Testing Library, and integration tests with Detox for E2E. I also document architecture decisions in ADRs. For CI/CD, I set up linting, tests, and build checks on every PR. Maintaining a consistent folder structure and using feature-based modules helps scalability.
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
At RubyLabs we’re looking for a Senior React Native Developer to join our growing engineering team and help lead our expansion into mobile. This is a role for someone who cares deeply about product quality, enjoys solving architectural challenges, and wants ownership over real features that users rely on.
You’ll play a key role in building and scaling our mobile applications, shaping the future of our mobile offering, and collaborating closely with backend and product teams to deliver a seamless, reliable, and high-performance user experience.
Key Responsibilities
Contribute to the development and delivery of new mobile product features.
Maintain and improve the existing React Native codebase, performance, and stability.
Define and evolve mobile architecture, system design, and technical strategy.
Partner with backend, product, and design teams to shape solutions that scale.
Drive reliability, performance, and observability standards on mobile.
Own production debugging, incident investigation, and root cause analysis.
Guide improvements in build systems, CI/CD, releases, testing, and app store deployments.
Support hiring and help grow a world-class mobile engineering team.
Champion performance across rendering, navigation, latency, memory, offline behavior, caching, and real-time experiences.
Qualifications
5+ years of experience building mobile applications, with significant React Native experience.
Experience mentoring engineers through code reviews, architecture, and incident response is a strong plus.
Strong understanding of mobile system design, component architecture, state management, navigation patterns, and performance trade-offs.
Experience optimizing UI performance, memory usage, rendering efficiency, and startup time.
Deep knowledge of React internals and rendering behavior (hooks, reconciliation, lifecycle, render cost).
Experience working with native modules and iOS/Android bridging.
Shipped and maintained apps on the App Store and Google Play.
Experience with CI/CD, builds, release automation, and OTA updates (EAS, CodePush, or similar).
Experience implementing monitoring and observability (Sentry, OpenTelemetry, crash reporting, performance tracing).
Demonstrated ownership of edge cases, distributed failure modes, degraded APIs, offline sync, and recovery UX.
Demonstrated ability to lead architecture or technical strategy for a mobile app or major feature.
Maintains high standards for clean code, SOLID principles, maintainability, and documentation.
Nice to have
Experience in startup or high-ownership product teams.
Experience scaling real-time or multi-region mobile architectures.
Experience designing or building design systems, shared component libraries, or mobile platform foundations.
Experience improving mobile security, analytics, performance profiling, and release automation.
Knowledge of edge caching, streaming real-time events, WebSockets, or offline-first architectures.
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)
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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