SENIOR MOBILE ENGINEER, REACT NATIVE (FOUNDING TEAM)

ABOUT ZAHLN
Zahln, by Zysygy, is building a zero-fee payment network for Germany on European banking rails. Merchants pay no transaction fees. No card networks, no hardware, just a phone.

Nearly every digital payment in Germany today moves over infrastructure owned outside Europe, and a share of each one leaves the continent as fees. We are building the alternative on European rails: a fully software-based merchant POS and a consumer super-app for everyday financial life, payments, transport, utilities and government services in one place, settling account to account over SEPA Instant, with European data residency by design. Think what UPI did for India. We are doing it for Germany, on infrastructure Europe controls.

THE ROLE
You are our first frontend engineer. You build every interface Zahln has, from an empty repository: the consumer and merchant apps on iOS and Android, and the web tools our team uses to run the network. There is no existing codebase, design system or release process. You build all three, and you bring the experience to make those decisions without being told how. You also sit between product, design and backend, making sure that whenever money moves, what the user sees is fast, clear and correct.

WHAT YOU WILL DO

Mobile

  • Consumer app: Build onboarding, wallet, payment and account flows for iOS and Android from one React Native codebase.
  • Payment experience: Make the moment of paying fast and unambiguous, including what the user sees when the network drops or a step fails halfway.
  • Merchant app: Build the flow merchants use to accept payments, confirm them and issue refunds.
  • Device capabilities: Work with camera and QR, NFC, biometrics, secure storage and push notifications, and drop to native code when it is genuinely needed.
  • Releases: Own store submission, signing, versioning, staged rollouts and forced updates on both platforms.
  • Safe releases: Build the app so it can be corrected without a new release: feature flags, kill switches, server-driven configuration and forced updates. You cannot hotfix a phone.
  • Authentication: Handle strong customer authentication in practice: when to ask for re-authentication, what happens when biometrics fail, and how a session survives an app switch safely.

Web

  • Internal tools: Build the web console our team uses to find users, merchants and transactions and resolve issues quickly.
  • Customer-facing web: Build web surfaces for business customers as they come on board.

Foundations

  • Architecture: Set the frontend architecture and standards that future engineers will build on.
  • Design system: Build one design system shared across app and web, together with our designer.
  • Quality and security: Automated testing, crash and performance monitoring, and secure handling of sessions, tokens and personal data.
  • Accessibility and languages: Accessible interfaces in German and English from the first screen.

WHO YOU ARE

  • 4+ years building production apps, with genuine depth in React Native and TypeScript. Not React with some exposure to mobile.
  • You have shipped to both the App Store and Google Play, handled a rejection, and maintained what you released.
  • Comfortable building web applications in React. You do not need to be a web specialist, but a data-heavy internal tool should not slow you down.
  • You think in states, not screens. Asked to describe a payment screen, you also describe pending, failed, expired and refunded.
  • You know why an automatic retry on a payment request is dangerous, and how an app should behave on an unreliable network.
  • You measure performance instead of assuming it: startup time, frame rate, time to confirmation.
  • You make product and design decisions on your own and can defend them, including to the founders.
  • You write clearly and work well remotely across time zones.
  • You use AI tooling seriously in your workflow and know where it produces confident nonsense.
  • You want to build a company, not fill a position.
  • You are comfortable at the device layer: push reliability, deep links, background states and secure storage, and you know when dropping below React Native is the right call and when it is showing off.
  • You know mobile security in practice: certificate pinning, keychain and keystore, integrity checks, protecting sensitive screens, and logging that never exposes a token or a balance.
  • You handle personal data carefully. You understand GDPR and keep user data in Europe, including in analytics and crash reporting.
  • You handle personal data carefully. You understand GDPR and keep user data in Europe, including in analytics and crash reporting.

STRONG BONUS (NOT REQUIRED)

  • Experience on payments, fintech or banking apps, where a bug costs someone money rather than time. Time at or around India's payments companies is directly relevant.
  • You have shipped NFC, biometrics or secure payment flows on iOS or Android.
  • You have built an admin, merchant or back-office console.
  • You have built or maintained a design system used across more than one surface.
  • You have run releases under pressure: phased rollout, rollback, an emergency fix on a Friday.
  • Accessibility and localisation in practice, not just in principle.
  • You design as well as build, in Figma or directly in code.
  • You know exactly what Apple and Google allow third-party apps to do with NFC.

HOW WE WILL MEASURE YOU

  • Apps that ship on schedule and stay stable in production.
  • Payments that feel instant and never leave a user unsure what happened.
  • Internal tools that let our team resolve an issue in minutes.
  • Over time, a codebase and standards the next engineers can build on without rewriting.

WHAT YOU GET

  • Real ownership. Every interface of the company is yours from day one: iOS, Android and web. Not a feature team inside someone else's architecture.
  • Something that matters. You help build European payment infrastructure that businesses and people use every day, instead of polishing a product that already exists.
  • Your work, in users' hands fast. No layers of approval between a decision and a release. What you build this month is in people's hands within weeks.
  • A seat at the table. You work directly with the founders on product and technical decisions, and you have a real say in a stack you will live inside for years.
  • Room to grow with the company. As the team grows, you set the standards and shape the frontend team that follows.
  • A small team that moves. People who left stable paths to build a faster, simpler way to move money in Europe. Less bureaucracy, more momentum.

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