Senior Mobile Engineer (Flutter + iOS)

N-iX is a global software development service company that helps businesses across the globe create next-generation software products. Founded in 2002, we unite 2,400+ tech-savvy professionals across 40+ countries, working on impactful projects for industry leaders and Fortune 500 companies. Our expertise spans cloud, data, AI/ML, embedded software, IoT, and more, driving digital transformation across finance, manufacturing, telecom, healthcare, and other industries. Join N-iX and become part of a team where your ideas make a real impact. Our client is a leading, fully regulated US-based digital asset trading platform. They provide secure, low-latency access to cryptocurrency markets, acting as a bridge between traditional finance and the Web3 ecosystem. The Senior Mobile Engineer will play a pivotal role in transitioning the core mobile platform from native environments to a unified Flutter/Dart codebase. You will maintain the stability of the existing production iOS app while architecting and developing robust, scalable cross-platform features, ensuring a seamless migration process. Key Responsibilities: Maintain, enhance, and support our production native iOS application written in Swift. Collaborate on the design and development of a new Flutter/Dart codebase, ensuring performance and scalability. Own end-to-end delivery of mobile features, including development, testing, release, and ongoing support Build clean, modular, and reusable code to support scalable mobile architecture Collaborate with Product, Design, and Backend teams to define requirements and deliver high-quality features Optimize app performance, responsiveness, and reliability across a range of iOS devices Integrate RESTful APIs and ensure efficient data handling and state management Participate in code reviews and contribute to maintaining high standards of code quality and maintainability Identify and resolve performance bottlenecks, bugs, and technical issues Partner with QA and DevOps to support CI/CD pipelines, automated testing, and release processes Mentor junior engineers and contribute to a culture of continuous improvement Required Qualifications: Bachelor's degree in Computer Science or a related field; 5+ years in mobile development experience: 3+ years of native iOS (Swift) and 2+ years of Flutter/Dart (or strong cross-platform experience with proven learning track). Strong expertise in iOS development: Swift, UIKit/SwiftUI, architecture patterns (MVC, MVVM, VIPER, Clean), and modern concurrency (Combine, async/await) Hands-on Flutter experience: Dart, state management (Provider, Riverpod, Bloc, or GetX), and native–Flutter integration (platform channels/pigeon). Proven experience in app migration or hybrid architectures (native + Flutter), ensuring production stability during transition. Solid experience with REST APIs, async data handling, and state management across mobile layers. Experience with performance optimization and debugging tools (Xcode Instruments, Flutter DevTools, Firebase). Strong testing practices: XCTest/XCUITest, flutter_test/integration_test, CI-integrated automation. Familiarity with mobile security best practices (secure storage, biometrics, certificate pinning, auth flows). Experience with Git and CI/CD pipelines (Fastlane, Bitrise, GitHub Actions, Codemagic), App Store processes (TestFlight, App Store Connect). Experience working in FinTech, banking, trading, or other highly regulated environments, with a strong collaboration and mentorship mindset across cross-functional teams (Product, Design, Backend, QA, Android); Upper-Intermediate level of English or higher. Preferred Qualifications: Exposure to Android (Kotlin) and full cross-platform transitions; mobile analytics/push notifications (APNs, FCM); and crypto / Web3 mobile integrations - wallet flows, WalletConnect, MetaMask SDK, transaction signing, on-chain data display. We offer*: Flexible working format - remote, office-based or flexible A competitive salary and good compensation package Personalized career growth Professional development tools (mentorship program, tech talks and trainings, centers of excellence, and more) Active tech communities with regular knowledge sharing Education reimbursement Memorable anniversary presents Corporate events and team buildings Other location-specific benefits not applicable for freelancers