Senior Full-Stack Engineer (Mobile apps for Banking, Trading and FinTech)

About the Company

Our client is a developer of scalable fintech and trading platforms, providing enterprise-grade infrastructure to global partners. As part of a major initiative to integrate our platform's trading infrastructure into the applications and internal services of a large bank, we are opening a position for a Senior Full-Stack Engineer (Mobile & Backend focus).

The core challenge of this role is designing and developing fault-tolerant mobile trading modules and ensuring their seamless, high-load integration with both the bank’s and our platform’s server-side architectures.

What You'll Do

• Mobile & Server Integration: Develop and implement cross-platform mobile solutions (React Native) and backend services to embed our trading engine into the banking environment.
• High-Load Mobile Architecture: Ensure minimal interface response times and flawless processing of streaming quotes, charts, and orders via WebSockets on mobile clients.
• Backend Services: Build robust API gateways, data adapters, and integration layers connecting the mobile client with banking services and our core platform.
• Client Collaboration: Participate in technical sessions with the CTO, bank architects, and client engineers to align on security protocols and mobile client requirements.
• Security & Optimization: Ensure the mobile application meets strict banking security standards (encryption, biometrics, secure session management).

AI-Native Approach (Strict Requirement)

Active, practical use of AI is a mandatory baseline requirement. We expect you to treat AI as a fundamental part of your development process:

• Continuous work with cutting-edge tools (Claude, Cursor, Copilot, agentic scripts) to accelerate system design, code generation, refactoring, and automated testing.
• The ability to critically verify AI outputs and leverage them to multiply the delivery speed of complex features.

Who You Are

• Domain Expert: Practical experience in trading, banking products, fintech, or payment solutions (understanding the nuances of transactions, authorization, and financial data).
• High-Load Mobile Experience: Expertise in handling intensive real-time event streams and maintaining strict connection stability on mobile devices.
• Confident Communicator: Comfortable speaking directly at a high technical level with CTOs and enterprise banking leads.
• Fast Learner: Capable of quickly mastering the architectural specifics of our core product with the support of our internal engineering team.

Qualifications

• English: Upper-Intermediate or Fluent (strong verbal and written skills for daily client communication).
• Experience: 5+ years of commercial development experience, balancing mobile and backend responsibilities.
• Mobile Stack: Excellent command of React Native and TypeScript, with a deep understanding of iOS/Android platform specifics, native modules, and mobile rendering optimization.
• Backend Stack: Solid backend development experience (Node.js/TypeScript or similar enterprise stacks), with proven ability to build REST/GraphQL APIs and handle WebSocket communication.
• Infrastructure & Security: Understanding of mobile data protection principles, caching strategies, background task management, and push notifications.

Bonus Points:

• Experience embedding modules (SDKs/white-label solutions) into existing large-scale mobile banking applications.
• Practical familiarity with OAuth2/mTLS authorization protocols within the banking sector.

We Offer

• Flexibility & Hubs: Flexible schedule with hubs in Ukraine and Poland (Wroclaw).
• Health & Wellness: Medical Insurance (Ukraine) and Multisport program (Poland).
• Time Off: Paid vacations, sick leave, and all public holidays.
• Growth: Mentorship programs, access to educational platforms, and English classes (up to 3 times a week).
• Equipment: Modern development hardware provided by the company.
• Support: Tax and accounting support for specialists in Ukraine.
• Culture & Perks: Regular team-building activities, meetups, and a transparent bonus system.