Senior Mobile App Developer

OnBuy is on a mission to disrupt the eCommerce space with a fair, transparent, and seller-friendly marketplace. As we continue to scale, we’re investing in our mobile experience to better serve our customers and sellers. We're now looking for a talented Senior Mobile App Developer to join our growing tech team and lead the evolution of our mobile apps.

Key Responsibilities: 

• Lead the development and maintenance of high-quality mobile applications from concept through to launch.
• Build robust, scalable, and performant apps for both iOS and Android platforms using Swift and Kotlin.
• Collaborate with backend and frontend teams to ensure seamless integration across the full stack.
• Implement and maintain WebView-based functionality while planning for a transition to more native app features.
• Integrate with Firebase services including Cloud Messaging, Realtime Database, and App Distribution.
• Manage app deployment pipelines using CI/CD tools like Fastlane and GitLab CI, including code signing and store submissions.
• Ensure secure coding practices and compliance with platform guidelines.
• Debug and resolve issues using platform-specific tools and logs.
• Implement features such as push notifications, deep linking, and gesture recognition.
• Support the wider development team with front-end tasks when needed, using HTML, CSS, and JavaScript.
• Contribute to architectural decisions and help shape the future of mobile at OnBuy

Experience and Skills: 

Essential

• Proven experience developing and launching mobile apps for both iOS and Android.
• Frontend experience (with CSS, HTML and JavaScript. Vue.js — a big bonus)
• Strong proficiency in Swift (iOS) and Kotlin
• Experience working with Android Studio, Xcode, and Apple Developer Console.
• Solid understanding of the differences between iOS and Android ecosystems.
• Experience with Firebase, including FCM, App Distribution, and Realtime Database.
• Familiarity with CI/CD pipelines, automated testing, and deployment processes.
• Experience using tools like Fastlane to automate testing, building, signing, and publishing.
• Comfortable working in a start-up or scale-up environment with a fast-paced, agile approach.
• Excellent problem-solving skills and the ability to think algorithmically.
• Working knowledge of HTML, CSS, and JavaScript to support front-end development when required.

Desirable

• Full stack experience (including backend)
• Experience with hybrid frameworks (e.g. React Native, Flutter) and integrating native functionality.
• Familiarity with analytics tools and performance monitoring for mobile apps.
• Contributions to open-source projects or a portfolio of published apps.

The salary range on offer for this role is £55,000 - £60,000 per annum, depending on experience.

We also offer the following benefits:

• 25 days annual leave + Bank Holidays
• 1 extra day off for your Birthday
• Employee Assistance Programme
• Perks at Work benefit platform
• Opportunities for career development and progression

Plus in return for helping us to grow, we’ll offer you company equity, meaning you own a piece of this business we are all working so hard to build.

Our Commitment

OnBuy is an equal opportunities employer. We are dedicated to creating a fair and transparent workforce, starting with a recruitment process that does not discriminate on the basis of gender, sexual orientation, marital or civil partnership status, pregnancy or maternity, gender reassignment, race, colour, nationality, ethnic or national origin, religion or belief, disability, or age.