Senior React Native Engineer, Fintech App (IOS Android Cross-Platform, Expo Bare Workflow)

Senior React Native Engineer, Fintech App (Genuine Cross-Platform, Expo Bare Workflow) Summary We aim to solve people's lack of time to invest idle cash. The aim is to build a UK fintech mobile app (cash optimisation platform, on FCA-authorisation track, targeting September 2026), React Native 0.81, Expo 54, bare workflow, TypeScript. We are looking for an experienced cross platform front end engineer to take over active development on an established monorepo. Auth flows, PIN handling, core navigation, and EAS build pipeline are already built and verified on both platforms. Cross-platform requirement: This app ships on iOS and Android equally, from day one, every sprint. iOS-first development with Android trailing behind, discovered late, or left unverified is not acceptable practice on this project. Every feature and every build needs demonstrable parity on both platforms before it's considered done. Tech stack React Native 0.81, Expo 54 (bare workflow), Expo Router v5 TypeScript, TanStack Query, Zustand Auth0 / OAuth2 / OIDC, Expo SecureStore, React Native Keychain Reanimated, Skia charts Turbo monorepo, GitHub Actions, EAS Build (both iOS and Android build profiles maintained and tested continuously) Backend (context only): Java 21, Spring Boot, PostgreSQL, Azure Non-negotiables on this codebase No parseFloat/toFixed/floating-point on any monetary value. Integer pence throughout. Sensitive data (PINs, tokens) never in navigation route params. Ephemeral state only, cleared on abandon/cancel/unmount. Async failure paths must surface, never fail silently. Design tokens consumed from confirmed Figma/Token Studio exports only, never estimated ahead of the designer's confirmed values. Accessibility roles must match actual UI behaviour. All platform accounts, repositories, and credentials created in the course of work belong to the company from creation, never held under a personal account. How we work All code review via GitHub PR comments, permanent audit trail. When you report something as fixed, done, or working, we expect evidence: a commit hash, a build artefact, a passing test. Not purely a description. Minimum four hours' overlap with UK. Monday to Friday. Founder iterates 6 to 7am UK mornings, and 9 to 10pm UK evenings. Weekends, 10am to midday UK. Same-day response during active review cycles is expected. What you'll be doing End Goal is to complete mobile prototype with readiness for MVP at regulatory approval. Continuing feature build-out (goal-tracking, trade screens, ongoing auth hardening) with equal iOS and Android delivery Working from a confirmed design system, iterating with founder and UX. never ahead of confirmed exports. Writing test coverage alongside logic changes Maintaining CI/build pipeline health on both platforms Ideal candidate Minimum 5 years' React Native-specific experience, within 7–8 years' total software/mobile engineering experience Fintech, payments, or other FCA/regulated-industry experience strongly desirable. This platform is on an active FCA authorisation track; familiarity with regulated data handling and audit trail requirements is an advantage. Demonstrable, shipped cross-platform apps Comfortable owning the full EAS build pipeline for both platforms independently Strong TypeScript, correct async and React hooks handling Minimum 4 hours' daily overlap with UK business hours Engagement Ongoing, part-time or full-time considered Rate: USD 20–35/hour depending on experience, with genuine fintech/regulated background weighted favourably Paid milestone-based, written scope per milestone, released on verified sign-off on both platforms To apply, include: 1.Links to two apps you've personally shipped to both the App Store and Google Play, not one platform only 2.Describe a real iOS/Android divergence bug you've hit, what caused it, and how you fixed it 3.Your working hours and typical weekday and weekend response time during active review cycles 4.One example of telling a client "this isn't done yet" rather than rounding up