As Principal Software Engineer, you'll work directly with the Head of FinTech Engineering and business leadership, translating critical business goals - new product lines, regulatory deadlines, growth targets - into architecture decisions and roadmap input. You'll be the final word on cross-domain technical questions that no single team or Staff Engineer can resolve alone. → Hybrid working model: preferably 1 day per week in the Warsaw or Cracow office .   Responsibilities: Serve as the single cross-domain technical authority, arbitrating architecture decisions across Payments Core, Merchant, and Consumer platform areas Partner directly with the Head of Engineering and business leadership to turn business strategy into technical roadmap input Author Architecture Decision Records (ADRs) and RFCs for organisation-wide decisions, with reasoning accessible to both engineers and business stakeholders Own the agentic engineering harness at an organisational level — design, instrument, and continuously improve AI-assisted engineering workflows based on real production data Identify and drive the adoption or deprecation of patterns across all teams, building the case and sequencing change without direct authority Mentor Staff Engineers and Engineering Managers on architecture craft, technical communication, and agentic tooling