Staff Software Engineer, Frontend - Fintech Platform (m/f/n)

InPost Pay is building its own fintech platform from the ground up. It’s a large-scale, international initiative where engineers will have the opportunity to shape the architecture, build core fintech components, and create solutions designed to operate at InPost’s scale. We’re building a lean, highly effective engineering organization in Poland, with AI-native engineering at its core. We’re looking for strong engineers who are comfortable with agentic engineering, from experienced professionals building complex systems and engineering tooling to a new generation of engineers who have embraced AI-driven development from the start of their careers. InPost's FinTech Platform team is looking for a Staff Engineer to define the technical direction for one of our platform areas - Payments Core, Merchant, or Consumer. You'll multiply team output through architecture clarity, engineering standards, and cross-team technical leadership, while helping evolve our agentic engineering harness in a data-driven way. You'll own the evolution of fundamental technology decisions across your area - ensuring they're sound, defensible, and viable for the long term - and act as the technical throughline between engineering teams, product strategy, and the organisation's wider architecture standards. → Hybrid working model: preferably 1 day per week in the Warsaw or Cracow office. Responsibilities: - Define and maintain frontend architecture across the area: component architecture, design-system boundaries, micro-frontend patterns, client-side state management, and performance budgets across multiple teams - Author Architecture Decision Records (ADRs) and RFCs for frontend decisions, facilitating technical decision-making across teams with documented reasoning and clear trade-off analysis - Evaluate and decide on fundamental frontend technology trade-offs: framework and library selection, build tooling, rendering strategy (SSR / CSR / ISR), and accessibility standards - Own the evolution of the agentic development harness for frontend workflows — instrument it, measure adoption and friction, and drive improvements with data - Drive org-wide technical change: identify frontend patterns and design-system components to adopt or deprecate broadly, build the case, and see adoption through across teams without direct authority - Provide technical input into product strategy; mentor Staff-track engineers through design reviews, pairing, and technical writing feedback - 8+ years in software engineering, including 2+ years in cross-team technical leadership or architecture authority - 3+ years building customer-facing or merchant-facing products in payments or fintech - Expert-level experience with a modern frontend framework (e.g. React) and TypeScript at scale - Design-system and component-architecture experience across multiple teams or products - Micro-frontend architecture and client-side state management patterns - Performance engineering expertise — Core Web Vitals, bundle optimisation, and rendering-strategy trade-offs (SSR / CSR / ISR) - Accessibility standards (WCAG) built into architecture, not bolted on - API-consumption patterns: REST, GraphQL, async, and event-based contracts - Experience designing or evolving an agentic engineering harness for frontend workflows — instrumentation, adoption measurement, iteration - Excellent technical writing — ADRs, RFCs, and design docs for multiple audiences - English proficiency at B2 or above - University degree in Computer Science, IT, or a related field Nice to have: - 2+ years in platform or internal developer tooling engineering - 1+ years of agentic/LLM system design experience - 2+ years in BNPL or lending domain product experience - Mobile app architecture (e.g. React Native) alongside web - Real-time UI patterns (WebSockets, streaming updates) - Internationalisation / localisation architecture at scale - Open-source contributions or technical publishing - Polish language skills - Opportunity to work in a diverse, international, and cross-functional environment, along with leading experts. - You work and learn from a senior leader and their leadership team, expanding your experience and exposure in the e-commerce and logistics industries. - InPost is a growing company that offers its people an increasing number of opportunities in several locations in Europe. - Fulfilling careers with a range of benefits for people and investing in providing training opportunities for their development. - You will feel a part of the InPost community that makes an impact on sustainability, convenient deliveries, and the circular economy every day. - Excellent working environment and flexible hours - We offer B2B type of contract