Senior Fullstack Engineer (Kotlin + React) – API-First, Warsaw Visits

Poland and Middle-Eastern Europe; Poland; On-site; PLN 200,000 - 360,000; Full time

Job summary

Xebia, a global AI-first, digital transformation and engineering partner, is hiring in Poland. The role focuses on designing and implementing REST APIs, leading integration architecture, and delivering backend services in Java/Kotlin plus modern frontend work in React and TypeScript.

The candidate will work with distributed systems, API-first design, OAuth 2.0/OpenID Connect, and contribute to engineering standards while collaborating across teams.

Qualifications

• Proven experience designing, building, and maintaining REST APIs.
• Hands-on API-first design with OpenAPI / Swagger.
• Strong React and TypeScript knowledge.
• Solid distributed systems and system integrations.
• Experience making architectural decisions and leading technical discussions.
• Good English (B2) and Polish (B1).
• Willingness to visit Warsaw office 1–2 per quarter.
• Work permit for EU and office in 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.
• 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.

Skills

Java

Kotlin

REST APIs design

OpenAPI / Swagger

React

TypeScript

Distributed systems

OAuth 2.0 / OpenID Connect

Architectural leadership

Communication & collaboration

English (B2)

Polish (B1)

Job description

Xebia, a global AI-first, digital transformation and engineering partner, is hiring in Poland. The role focuses on designing and implementing REST APIs, leading integration architecture, and delivering backend services in Java/Kotlin plus modern frontend work in React and TypeScript.

The candidate will work with distributed systems, API-first design, OAuth 2.0/OpenID Connect, and contribute to engineering standards while collaborating across teams.