Sr Staff Backend Engineer - Java Poland
Senior/Staff Backend Engineer owning Java services for Oscilar's AI risk-decisioning platform, used by banks and fintechs for real-time fraud, credit, and compliance decisions. Day to day: end-to-end feature ownership, low-latency streaming/data systems (Kafka, Flink, ClickHouse), AWS and Kubernetes, in a 100% remote Poland-based B2B contract role.
- Compensation
- PLN 32K–PLN 47K / mo
- Location
- Warszawa, Poland
- Work setup
- Remote
- Seniority
- Staff
- Employment
- Contract
- Experience
- 5+ years
- Category
- Backend
- Posted
Skills
Must have
- 5+ years of backend development with deep expertise in Java and its ecosystem
- Track record of taking work from initial concept to production with minimal hand-holding
- Comfortable with ambiguity; knows when to ask questions and when to make a call
- Solid experience building and operating low-latency, high-scale distributed systems in production
- Hands-on experience with AWS, microservices, and containers (Docker, Kubernetes)
- Experience with event streaming and data systems such as Kafka, ClickHouse, PostgreSQL, and Redis
- Good understanding of API design and security best practices
- Strong written and verbal communication skills
Nice to have
- Experience with Flink, Temporal, or Databricks
- Experience in fintech, fraud prevention, risk, or payments
- Degree in Computer Science, Software Engineering, or a related field
- Experience using AI coding agents (e.g. Claude Code) in day-to-day development
Full description
Location Remote (Poland) · B2B contract Shape the future of trust in the age of AI At Oscilar, were building the most advanced AI Risk Decisioning⢠Platform. Banks, fintechs, and digitally native organizations rely on us to manage their fraud, credit, and compliance risk with the power of AI. If youre passionate about solving complex problems and making the internet safer for everyone, this is your place. Why join us: Mission-driven teams: Work alongside industry veterans from Meta, Uber, Citi, and Confluent, all united by a shared goal to make the digital world safer. Ownership and impact: We believe in extreme ownership. Youll be empowered to take responsibility, move fast, and make decisions that drive our mission forward. Innovate at the cutting edge: Your work will shape how modern finance detects fraud and manages risk. Job Description As a Senior/Staff Backend Engineer, youll own critical parts of the platform that banks and fintechs use to make real-time fraud, credit, and compliance decisions. Youll join a small, senior team where your technical decisions have direct impact. What youll do Own features end to end: turn an idea or customer problem into a design, build it, ship it safely (GitHub Actions, feature flags with LaunchDarkly), and keep it running well in production. Build and scale the Java services at the core of our decisioning platform, where latency and reliability directly affect our customers. Work on real-time streaming and data systems (Kafka, Flink, ClickHouse, Databricks) handling high event volumes with tight latency requirements. Build reliable processes with workflow orchestration (e.g. Temporal). Make technical decisions, not just implement them: propose architecture, weigh trade-offs, and write design docs. Work directly with product, frontend, and customer-facing teams to understand the problem before writing code. Own production: monitoring, performance tuning, and fixing root causes, not symptoms. Raise the engineering bar through code reviews, knowledge sharing, and helping others grow. What were looking for 5+ years of backend development, with deep expertise in Java and its ecosystem. A track record of taking work from initial concept to production with minimal hand-holding. Youre comfortable with ambiguity and know when to ask questions and when to make a call. Solid experience building and operating low-latency, high-scale distributed systems in production. Hands-on experience with AWS, microservices, and containers (Docker, Kubernetes). Experience with event streaming and data systems such as Kafka, ClickHouse, PostgreSQL, and Redis. Good understanding of API design and security best practices. Strong written and verbal communication skills. We work async a lot, and Claude is part of how we work every day, connected to Slack, Notion, Linear, GitHub, etc. Nice to have (not required) Experience with Flink, Temporal, or Databricks. Experience in fintech, fraud prevention, risk, or payments. A degree in Computer Science, Software Engineering, or a related field. Experience using AI coding agents (e.g. Claude Code) in day-to-day development. Benefits Competitive salary: 32,000 â 47,000 PLN net/month + VAT (B2B). Remote-first culture: daily collaboration with a Poland-based, 100% remote team, and healthy overlap with our teams in Brazil and the US. Technical: AI-first company; both co-founders are engineers at heart, and over 50% of the company is Engineering and Product. Culture: Family-friendly environment; regular team events and offsites (2025: Mexico City, Mexico; 2026: Miami, Florida; 2027: Cancún, Mexico). Development: Unparalleled learning and professional development opportunities. Equipment: the latest MacBook, or a Linux machine if you prefer. This is a contractor relationship. Contractors are paid a flat monthly fee. Contractors may take time off with advance notice to the business. If you are passionate about backend development, real-time streaming, and scalable data systems, join us at Oscilar and make an impact.