Principal Software Engineer - Fintech Platform (m/f/n)

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
• 10+ years in software engineering, including 5+ years in cross-team technical leadership or architecture authority
• 5+ years designing distributed payments or fintech systems
• 3+ years of agentic/LLM engineering in production — shipped systems, not theoretical patterns
• Deep knowledge of distributed systems architecture: event sourcing, CQRS, domain events, saga pattern
• Experience designing APIs at an organisational boundary level — REST, async, and event-based contracts
• Strong grasp of database trade-offs (relational, time-series, document, ledger-style) and cloud architecture evaluation (AWS/GCP/Azure) at organisation scale
• Hands-on experience with multi-agent orchestration, tool-use patterns, context management, and evaluation harnesses for AI-assisted engineering workflows
• Excellent technical writing for mixed audiences — ADRs and RFCs that work for engineers and business leadership alike
• English proficiency at B2 or above
• University degree in Computer Science, IT, or a related field

Nice to have:

• 3+ years in platform or internal developer tooling engineering
• 1+ years of agentic/LLM system design experience
• PCI DSS / PSD2 architecture compliance experience from the design phase
• BNPL or lending domain architecture experience
• Open-source contributions or external technical publishing
• Experience building or scaling an internal developer platform
• Formal mentorship of Staff-level or EM-track engineers
• 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