Senior Mobile and Web Application Developer

Founded in 2022, EQWIN is a fast-growing startup reimagining the horse racing experience. Our app bridges the real and digital worlds, allowing users to create and manage their own virtual racing stables built from real racehorses whose value evolves with live performance.

With over 25,000 users in France and a recent acquisition by a U.S. investment fund (April 2025), we’re now preparing for international expansion.

Our mission: make horse racing modern, fun, and accessible to a new generation of fans.

Our mobile app is built with React Native / TypeScript. A web client is being developed in parallel with React 19, with maximum reuse of components, business logic and design system between mobile and web. The backend exposes a GraphQL API and REST.

A quick note for candidates:

The description below is a picture of our ideal candidate. If you cover at least half and can learn the rest quickly, you definitely need to apply!

Responsibilities

• Develop robust and scalable cross-platform mobile applications using React Native
• Develop robust and scalable web-application using React
• Integrate with API (GraphQL and REST)
• Implement and maintain payment flows with PSPs (including SCA / 3-DS 2)
• Maintain code quality
• Build and evolve reusing shared packages/components

Mobile application technology stack:

• React Native + Expo SDK
• TypeScript

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• React Navigation
• TanStack Query
• Apollo Client (GraphQL client)
• Jotai + Zustand
• GraphQL + Hasura SDK
• WebSocket
• Firebase (Analytics, Crashlytics, Messaging, Remote Config)
• MangoPay SDK
• React Native Reanimated (animations)
• React Native Skia (custom graphics)
• Expo Notifications
• Expo Secure Store
• Biometric Authentication
• Sentry (error monitoring)
• EAS Build (app building and deployment)

Requirements (must-have skills):

• Excellent knowledge of React Native for iOS and Android
• Knowledge of React 19 for web-application
• Experience reusing code between mobile and web

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• GraphQL client expertise
• Payment integrations on the client (SDK / WebView, SCA / 3-DS 2 flows, clear UX around retries / errors)
• Performance optimization
• Push notifications and deep / universal links
• Testing culture: unit / integration and practical e2e coverage integrated into CI
• Client-side security & privacy: safe handling of sensitive data, correct token / session management, TLS / certificate validation, permissions and consent texts
• Communication: writing clear technical specs (RFC), doing code reviews, collaborating with backend / DevOps / product
• English - B2+: documentation and periodic technical calls

Nice to have (technologies and skills):

• Observability & analytics: crash reporting, product analytics, A / B experiments; dashboards and alerting on product metrics
• Modern RN capabilities: New Architecture (Fabric / TurboModules), Hermes / JSI, native modules (Swift / Kotlin)
• Experience with multiple PSPs and payment orchestration; understanding of KYC / AML constraints on the client side
• Russian - B2+: for technical calls

Terms

• Format: B2B (contractor), fully remote from any location (work from anywhere). Upon mutual interest, later involvement in additional company projects is possible and, subject to requirements, a transition to an employment contract with a French company.
• Workload: start part-time with an option to move to full-time; during the part-time period, combining with another job is acceptable (subject to SLA and confidentiality).
• Compensation: EUR by contractor invoice, payment via SEPA / SWIFT or a licensed EMI (e.g., Wise). Ability to receive payments from France to a B2B (contractor) account is required.