About this role.
Ruby Labs is seeking a Senior iOS Engineer to build and maintain high-performance B2C mobile products, likely with subscription-based revenue models. The role requires advanced Swift expertise, including Swift Concurrency, SwiftUI/UIKit interoperability, StoreKit 2, scalable architecture, and modularization. The engineer will own feature delivery, code quality, CI/CD, automated testing, App Store distribution, and performance optimization while partnering closely with product and engineering colleagues. This is a remote independent-contractor opportunity for candidates within approximately four hours of CET and is positioned as a fast-paced, high-accountability environment.
Role DNA
A quick view of the complexity, pace, ownership and collaboration implied by the job description.
Job Complexity
5/5Pace & Pressure
5/5Autonomy Level
5/5Communication Load
4/5Salary analysis
Estimated compensation compared with the broader US market for similar roles.
Core skills
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Cover letter sample
Dear Hiring Team,
I am excited to apply for the Senior iOS Engineer role at Ruby Labs. With extensive experience building scalable consumer iOS applications in Swift, I can contribute strong ownership across architecture, subscription experiences, performance optimization, and reliable App Store delivery.
- Advanced Swift, SwiftUI/UIKit, Swift Concurrency, StoreKit 2, and modular mobile architecture
- Hands-on CI/CD, automated testing, Instruments profiling, analytics, and feature experimentation
I work effectively in fast-moving cross-functional teams, translating product priorities into polished, measurable mobile experiences. I would welcome the opportunity to help Ruby Labs build high-performing subscription products and deliver impactful features for its customers.
Sample interview questions
I would describe a recent iOS feature or app area I owned end to end, including the architecture selected, key technical trade-offs, testing strategy, release process, and the product or performance outcome achieved.
I would use StoreKit 2 transaction verification, maintain a clear entitlement model, handle upgrades, downgrades, renewals, and billing failures, and reconcile client-side status with secure server-side notifications or a provider such as RevenueCat.
I would select SwiftUI for declarative, state-driven screens and fast iteration, while retaining UIKit where mature components, advanced navigation, or specialized integrations are better supported. Clear boundaries, shared view models where appropriate, and incremental migration reduce interoperability risk.
I would begin with reproducible metrics and Instruments, using Time Profiler, Allocations, Leaks, Hangs, and rendering tools to isolate the bottleneck. I would then validate improvements with before-and-after measurements, automated regression coverage, and monitoring in production.
I would create modular boundaries around features and core services, use dependency injection and protocol-based interfaces for testability, enforce code-review standards, and automate builds, tests, signing, and TestFlight distribution through CI/CD.
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 iOS 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 Swift and iOS development best practices will be instrumental in driving innovation and maintaining our position as a leader in the App Store.
Key Responsibilities
Develop and maintain a high-quality iOS 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, launch time, rendering, battery).
Stay up to date with the latest iOS development trends and integrate relevant advancements.
Qualifications
5+ years of professional iOS development experience.
Experience with B2C mobile apps built on subscription business models.
Expert proficiency in Swift (protocol-oriented design, generics, value semantics, async/await, structured concurrency, actors).
Strong command of StoreKit 2 and subscription lifecycle: purchase flows, receipt/transaction validation, entitlement management, offer codes, and server-to-server notifications (with RevenueCat or a custom equivalent).
Deep understanding of UIKit and SwiftUI, including interoperability, when to use each, and SwiftUI state management (@State, @Observable, @Environment).
Solid grasp of architecture patterns (MVVM, Clean Architecture, Composable Architecture) and modularization for large codebases (SPM modules, feature isolation).
Experience with Combine and/or Swift Concurrency for reactive and async data flows.
Proficiency with CI/CD (Xcode Cloud, Fastlane, Bitrise, or GitHub Actions), Gitflow, code signing/provisioning automation, and TestFlight distribution.
Automated testing experience: XCTest, XCUITest, snapshot testing, and dependency injection for testability.
Strong debugging and profiling skills with Instruments (Time Profiler, Allocations, Leaks, Hangs).
Experience integrating AI-driven features and/or AI-assisted development workflows.
Familiarity with analytics, crash reporting, and A/B testing / feature-flag tooling
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 (60 minutes)
Final Interview (30 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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