Senior Kotlin & React Fullstack Lead - API-First AI-Ready

Poland and Eastern Europe; Poland; Hybrid; PLN 180,000 - 300,000; Full time

Job summary

Xebia is a global AI-first, digital transformation partner seeking an experienced API-focused backend engineer to lead integrations with external partners. You will define API contracts, lead architectural decisions, and develop services in Java/Kotlin while delivering modern web apps with React and TypeScript.

The role requires strong API design skills, distributed systems expertise, and the ability to work across EU regions, including occasional visits to Warsaw.

Qualifications

• Requires strong Java and Kotlin experience.
• Proven REST API design and maintenance experience.
• OpenAPI/Swagger practitioner.
• Excellent React and TypeScript knowledge.
• Understanding of distributed systems and integrations.
• Experience leading technical discussions and setting standards.
• English at min. B2, Polish at min. B1; willing to visit Warsaw office.
• EU work permit and ability to work from EU region.

Responsibilities

• 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.
• Leading technical discussions and supporting the team in sound engineering decisions.
• Working with distributed systems and complex system integrations.
• Participating in the on-call rotation.

Skills

Java

Kotlin

REST APIs

OpenAPI/Swagger

React

TypeScript

Distributed systems

OAuth 2.0/OpenID Connect

Architectural leadership

English

Polish

Warsaw visit readiness

Tools

GitHub Copilot

Cursor

Claude

Job description

Xebia is a global AI-first, digital transformation partner seeking an experienced API-focused backend engineer to lead integrations with external partners. You will define API contracts, lead architectural decisions, and develop services in Java/Kotlin while delivering modern web apps with React and TypeScript.

The role requires strong API design skills, distributed systems expertise, and the ability to work across EU regions, including occasional visits to Warsaw.