Senior Fullstack Engineer (Kotlin&React)

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

Poland

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.

In the CEE region, we’re a team of nearly 1,000 experts delivering modern applications, data platforms, and AI solutions for clients such as McLaren, Aviva, Deloitte, Spotify, Disney, ING, UPS, Tesco, Truecaller, AllSaints, Volotea, Schmitz Cargobull, Allegro, InPost, and many, many more. We work with leading technologies including AWS, Azure, GCP, Databricks, and Snowflake, and combine strong engineering culture with a consulting mindset and a continuous focus on growth and knowledge sharing.

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:

CVreview –HRcall –TechnicalInterview –ClientInterview –Decision