Senior Fullstack Engineer (Kotlin&React)

Xebia is a global AI-first, digital transformation, and engineering partner. With over 25 years of experience and a team of 5,000 professionals across 16 countries, we help organizations design and build scalable products, platforms, and data-driven solutions.

We specialize in Artificial Intelligence, Data and Cloud, Intelligent Automation, and Digital Products, combining deep technical expertise with a strong focus on engineering excellence and a people-first culture.

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 (e.g. Claude Code, GitHub Copilot, 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 min. B2 level,
• Polish at min. 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 more 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 (e.g. agent-based workflows, automation patterns, AI-augmented development), with a willingness to explore and experiment beyond standard approaches.

Recruitment Process:

CV review – HR call – Technical Interview – Client Interview – Decision