Senior Full-Stack Engineer (Java/Kotlin + React)

Quick Facts

• Senior Full-Stack Engineer focused on Java/Kotlin and React

Description

Build API-first RESTful services and partner integrations for external B2B teams, including flexible API contracts, developer documentation, and mock environments. Develop new large-scale services in a greenfield “startup-like” model and create web interfaces (checkout paths, landing pages, discovery hubs) integrated with the backend and the mobile app. Provide technical leadership and act as an architectural anchor connecting Java backend design with modern frontend development, using advanced AI-assisted engineering.

Responsibilities

• Design flexible API contracts for external B2B partners and support partner onboarding
• Write developer documentation and create mock environments for integrations
• Build large-scale services in a greenfield environment and evolve toward a super app concept
• Develop web interfaces and integrate the frontend with the backend and mobile app
• Lead technical discussions, define coding standards, and support engineering execution with the Engineering Manager

Requirements

• Deep, hands-on experience in Java and/or Kotlin, including designing, building, and scaling RESTful APIs with an API-first approach (OpenAPI/Swagger)
• Strong frontend skills with JavaScript/TypeScript and a modern framework (React preferred)
• Solid understanding of distributed systems, integration patterns, and secure authentication (OAuth 2.0, OpenID Connect)
• Experience in technical leadership and designing API contracts for external B2B partners
• Advanced use of AI in engineering work beyond code autocompletion
• Problem-solver mindset and flexibility in greenfield projects
• English at B2+ level
• Right to work in Poland

Benefits

• Health and sports benefits tailored to your needs
• Speed Coaching: short sessions to provide new perspectives and solutions
• Sports training with an internal team and opportunities to participate in competitions