Senior Frontend Lead Engineer

Company Description Estia Group is a future-driven fintech startup building a pioneering ecosystem of user-centric technologies. Born in Greece and built for the world, we design, operate, and scale real-world solutions that prioritize regulation, security, and seamless user experience. Our group operates across four pillars, Estia Tech, Estia Payments, Estia Exchange, and Estia Foundation working together to reshape the future of digital payments and smart living. At the heart of our innovation is Estia Payments, our upcoming digital payment platform designed to simplify how consumers and businesses manage everyday transactions. At Estia, we don’t follow trends we build what comes next. We’re creating technology with real-world impact, and we’re always looking for talented people who want to be part of something bigger. Role Description We're looking for a Senior Frontend Lead Engineer based in Greece who thrives on crafting seamless, secure user experiences and is eager to shape frontend architecture in a high-growth fintech environment. You'll lead development across our React Native mobile app and Next.js web portal, guide technical decision-making, and contribute to a team that values clean code, scalable systems, and real-world problem solving. What You’ll Do Design and develop frontend systems using React Native (mobile) and Next.js (web), with TypeScript strict mode, clean component architecture, and scalable state management via Redux Toolkit and RTK Query.Lead UI architecture, code quality, performance, and security best practices.Build real-time user experiences using WebSocket live transaction feeds and push notifications.Implement secure authentication flows end-to-end with AWS Cognito, refresh token rotation, biometric auth, and secure storage.Design and build complex UX flows for multi-step KYC/KYB onboarding, POS terminal interactions, NFC payments, QR code transactions, and dashboards.Apply mobile release engineering and manage iOS and Android CI/CD pipelines, code signing, App Store and Google Play publishing, and OTA update strategies.Ensure frontend resilience and handle API failure states, offline/network detection, retry logics, and optimistic UI updates.Implement idempotency at the UI layer and deduplicate transaction submissions, manage loading/error/success states, and prevent double-submission on critical flows.Design versioned API integration patterns, maintaining backward compatibility across app versions still in the field.Enforce observability on the frontend and structured error reporting, performance monitoring, and crash analytics across both platforms.Apply secure coding principles across all frontend layers with OWASP Mobile Top 10 compliance.Work with AWS services from the frontend perspective like Cognito, S3, CloudFront, SES-triggered flows, and API Gateway contracts.Participate in system modeling using architectural diagrams, component design documents, and RFC-style decisions for major frontend changes.Contribute to documentation, knowledge sharing, and continuous improvement of frontend engineering practices. Must-Have Qualifications 7+ years of hands-on frontend experience building production web and mobile applications.Strong proficiency with React Native (0.78+), Next.js 14/15 App Router, and TypeScript strict mode.Deep understanding of frontend architectural patterns, component-driven design, micro-frontend awareness, state machine-driven UI flows.Expertise with Redux Toolkit, RTK Query, and complex async state management including optimistic updates and cache invalidation.Experience designing and operating real-time frontend systems using WebSocket, including reconnection strategies and stale-data handling.Strong understanding of frontend security, JWT lifecycle, secure token storage, biometric auth flows, OWASP Mobile Top 10, and secrets management.Solid knowledge of mobile release engineering in iOS and Android CI/CD pipelines, code signing, App Store and Google Play publishing, and OTA update strategies.Experience with AWS Cognito, API Gateway, S3, and CloudFront from the frontend integration perspective.Familiarity with performance engineering, bundle analysis, Lighthouse CI, lazy loading, memory profiling, and render optimization.Strong understanding of API versioning and backward compatibility managing multiple app versions simultaneously in the field.Proven team lead experience with code reviews, sprint planning, and setting engineering standards in a fast-moving product team.Bachelor's degree in Computer Science, Software Engineering, or related field. Why Join Us? Work on mission-critical fintech systems with real-world, high-impact use cases.Be part of an ambitious team that values ownership, autonomy, and engineering excellence.Continuous training and professional development support.A culture that values diversity, inclusivity, and equal opportunity.Work in a company where your technical decisions shape the future of a payment ecosystem. To Apply Please submit the following as a single PDF: Cover letter explaining your motivation and why you are a strong fit.Résumé outlining your experience and achievements. Applications are reviewed on a rolling basis until the position is filled. While we appreciate all applications, we will contact only those selected.