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

InPost is building its own fintech platform from the ground up, a large-scale international initiative to shape architecture, build core fintech components, and create solutions at scale. The company is building a lean, highly effective engineering organization in Poland, focused on AI-native engineering.

• 8+ years in software engineering, including 2+ years in cross-team technical leadership or architecture authority
• 3+ years designing distributed payments or fintech systems
• Hands-on experience with multiple tech stacks and expertise in backend
• Solid grounding in distributed systems architecture: event sourcing, CQRS, domain events, saga pattern, state machine and financial entity lifecycle design
• Experience designing APIs at service-boundary level: REST, async, and event-based contracts
• Comfort with database trade-off reasoning (relational, time-series, document, ledger-style) and cloud architecture evaluation (AWS, GCP, Azure)
• Experience designing or evolving an agentic engineering harness — instrumentation, adoption measurement, iteration
• Working knowledge of LLM tool-use patterns and context management in engineering workflows
• Excellent technical writing skills for ADRs, RFCs, and design docs
• English proficiency at B2 or above

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 architecture
• PCI DSS / PSD2 architecture compliance experience
• Kafka or equivalent streaming architecture experience at scale
• Open-source contributions or technical publishing
• Polish language skills

• Define and maintain backend technical architecture: domain boundaries, event contracts, state machine patterns, data consistency models, cross-service API design across teams
• Author Architecture Decision Records (ADRs) and RFCs with documented reasoning and trade-off analysis
• Evaluate and decide on technology trade-offs: database selection, cloud services, message broker topology, consistency models for financial data
• Own evolution of the agentic development harness: instrument, measure adoption and friction, drive improvements
• Drive organization-wide technical change: identify patterns to adopt or deprecate, build case, ensure adoption without direct authority
• Provide technical input into product strategy
• Mentor Staff-track engineers through design reviews, pairing, and technical writing feedback