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

InPost 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.

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