Senior Full Stack Engineer — TypeScript / Next.js (100%, m/f/d)

You are the architect and builder of the customer-facing side of the LEASETEQ platform in Berlin, and the owner of our German market on it. You design the digital application journey and the portals that carry real customers, dealers and operations teams at production scale, and you make sure German credit rules, compliance requirements and dealer flows are represented correctly in a platform that also serves Switzerland and Austria. You work in a small, senior team where your decisions have direct product impact, and you naturally bring AI tooling into your daily engineering workflow without being asked.

What you will do

• Own the German market on our customer-facing platform: credit and compliance requirements, dealer flows, German copy, and the acceptance criteria that make them verifiable
• Design and build the digital application journey — multi-step forms, validation, resumable state, document upload, KYC steps and the unhappy paths users actually hit
• Build and maintain the customer, dealer and operations portals, including the operations board and the logic that decides where a case belongs
• Write the use-case and API layers behind the journey to our clean-architecture standard — this is a full-stack role, not a UI role
• Own field-level mapping into the CRM and the Flowable-based process engine — beneficial ownership, source of funds, origin of income, additional persons — where a wrong key is a compliance defect, not a cosmetic one
• Author specification-driven change proposals, and act as the named human approver for journey and mapping changes in the German market
• Grow end-to-end test coverage on the critical journeys: coverage is what licenses autonomous agent work in a module
• Work with our Berlin backend team on the seam between the orchestration core and the customer-facing platform, and with our Jakarta platform engineers who own the journey across all three markets
• Communicate clearly in German and English with engineering peers and business stakeholders

• 6+ years of full-stack TypeScript engineering, with recent production work in React and Next.js App Router — server components, server actions and route handlers, with a clear grasp of what runs where — is mandatory
• Fintech experience is mandatory: production work on a regulated financial product — leasing, lending, banking, payments or insurance — where money moved and a regulator could ask why
• Proven ownership of a complex multi-step onboarding or application flow is mandatory: validation strategy, partial persistence and resumption, conditional branching by market or product, document upload
• Real backend capability: use cases, repository implementations, API handlers and PostgreSQL / Prisma queries — roughly a 60/40 split toward the frontend, not 90/10
• State and data