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

Location: Hybrid work with preferably 1 day per week in the Warsaw or Cracow office, Poland.

Company

Building an in-house fintech platform from the ground up for large-scale international operations, with an AI-native engineering organization in Poland.

What you will do

• Define and maintain backend architecture across Payments Core, Merchant, or Consumer platform areas.
• Design domain boundaries, event contracts, state machine patterns, data consistency models, and cross-service APIs.
• Author ADRs and RFCs, facilitate technical decisions, and document trade-offs across teams.
• Evaluate databases, cloud services, message broker topologies, and consistency models for financial data.
• Evolve the agentic engineering harness through instrumentation, adoption measurement, and data-driven improvements.
• Drive organization-wide technical changes, contribute to product strategy, and mentor Staff-track engineers.

Requirements

• 8+ years of software engineering experience, including 2+ years of cross-team technical leadership or architecture authority.
• 3+ years designing distributed payments or fintech systems.
• Strong backend expertise with experience across multiple technology stacks.
• Experience with distributed systems architecture, including event sourcing, CQRS, domain events, saga patterns, and financial entity lifecycles.
• Experience designing REST, asynchronous, and event-based APIs, evaluating databases and cloud architectures, and writing ADRs, RFCs, and design documents.
• English proficiency at B2 or above.

Nice to have

• Platform or internal developer tooling engineering experience.
• Agentic or LLM system design experience and knowledge of LLM tool-use patterns.
• BNPL or lending domain architecture experience.
• PCI DSS or PSD2 architecture compliance experience.
• Kafka or equivalent streaming architecture experience, open-source contributions, technical publishing, or Polish language skills.

Culture & Benefits

• Diverse, international, and cross-functional environment.
• Exposure to e-commerce and logistics industries and collaboration with experienced technical leaders.
• Training and development opportunities.
• Flexible working hours and an excellent working environment.
• B2B contract offered.