Kotlin Multiplatform Engineer

Wittix is a licensed Lithuanian electronic money institution building the financial platform companies use instead of a bank: multi-currency accounts, real local IBANs across Europe, payments in 35 currencies, and Visa cards with spend controls built in.

Our mobile app isn't a companion to a web dashboard. It's where our customers run their money. Around 2,400 businesses in 23 countries move roughly €120M a month through us. Bank payments is the first layer; a much wider set of payment services is coming, and mobile is where most of it will land.

About the Role

We are looking for a strong Kotlin Multiplatform Engineer to join our mobile engineering team and help shape the architecture of the next generation of Wittix products.

This is an opportunity to have a direct impact on the architecture of a real world platform combining Kotlin Multiplatform, payments, AI, commerce, hardware, cloud infrastructure, and real time systems.

You don't need to have built a banking app before, but you should want to work somewhere correctness matters.

What you'll do

• Design and develop production applications using Kotlin Multiplatform

• Own and evolve the shared KMP architecture across the product

• Build reusable shared modules for:

• Domain and business logic

• Networking and API communication

• Data and persistence

• Authentication and authorization

• State management

• Synchronization

• error handling and observability

• Define clear boundaries between shared KMP code and platform-specific implementations

• Develop platform-specific integrations for Android and other supported platforms

• Implement authentication and payment authorization flows, including in-app approval of card payments (3-D Secure)

• Build card features against our issuing processor's APIs: activation, freeze, spend controls, Google Pay and Apple Pay

• Build real-time experiences connected to cloud services and event-driven backend systems

• Apply mobile security fundamentals: secure key storage, certificate pinning, device and app integrity checks

• Establish reusable libraries and engineering patterns for KMP development

• Debug complex production issues across shared and native code

• Collaborate closely with Backend, Product, QA, DevOps

• Participate in architectural decisions and technical design

What we're looking for

4+ years of professional mobile development, mostly Android

Strong Kotlin, including Coroutines and Flow

Strong hands-on experience with Kotlin Multiplatform, shipped to production

Strong understanding of modular architecture and the split between shared and platform-specific code

Experience with REST APIs and local persistence (SQLite / Room or equivalent)

Clean, testable architecture and meaningful tests

Enough Swift to read, debug and ship changes in an iOS codebase — or a clear appetite to get there quickly

Ability to make pragmatic architectural decisions in a real product

Working English.

Nice to have:

Banking, wallet, payments, or another regulated consumer app

Card issuing or issuer-processor APIs

Mobile CI/CD (continuous integration and delivery): signed builds, TestFlight and Play internal tracks

Why Join Wittix

You'll shape a Kotlin Multiplatform architecture on a live product, not a prototype. Real money, real customers, and the authority to decide what belongs in the shared layer.