👉 Senior Fullstack Engineer (Kotlin/React)

You will be

• Designing and developing APIs enabling integrations with external business partners
• Taking a technical lead in integration architecture and contributing to key architectural decisions
• Defining API contracts and following an API-first approach using OpenAPI / Swagger
• Developing backend services using Java and Kotlin
• Building modern web applications using React and TypeScript
• Defining and promoting software development standards and best practices
• Preparing and maintaining technical documentation
• Leading technical discussions and supporting the team in making sound engineering decisions
• Working with distributed systems and complex system integrations
• Participating in the on-call rotation

Your profile

• Strong commercial experience with Java and Kotlin
• Proven experience designing, building, and maintaining REST APIs
• Hands-on experience with API-first design and OpenAPI / Swagger
• Very good knowledge of React and TypeScript
• Solid understanding of distributed systems and system-to-system integrations
• Practical knowledge of OAuth 2.0 and OpenID Connect
• Practical experience using AI-powered assistants, such as Claude Code, GitHub Copilot, or Cursor, to improve productivity, quality, or decision-making in software delivery
• Experience making architectural decisions and leading technical discussions
• Experience defining development standards and providing technical leadership within a team
• Strong communication and collaboration skills
• English at minimum B2 level
• Polish at minimum B1 level
• Willingness to visit the client’s office in Warsaw 1–2 times per quarter
• Work from the European Union region and a work permit are required

Nice to have

• Experience with data security and regulatory compliance, particularly GDPR
• Experience with B2B integrations and working with external business partners
• Experience applying GenAI in a structured way within the SDLC, including defined workflows, prompt patterns, or tool integrations embedded into daily work
• Interest in and familiarity with emerging AI-driven practices, such as agent-based workflows, automation patterns, and AI-augmented development, with willingness to explore and experiment beyond standard approaches

Recruitment Process

• CV review
• HR Interview
• Technical Interview
• Client Interview
• Decision

Benefits

Development

• Development budgets of up to 6,800 PLN
• Funding for certifications, e.g. AWS and Azure
• Access to Udemy, O’Reilly (formerly Safari Books Online), and more
• Events and technology conferences
• Technology Guilds
• Internal training
• Xebia Upskill

Health

• Private medical healthcare
• Subsidized MultiSport card
• Mental Health Support