Fullstack Engineer

What you work on today shapes where you’ll be tomorrow.

Looking for your next challenge as a Fullstack Engineer (Java/Kotlin + React)? We may have the right opportunity for you.

At B3, we start with people and their experience. We match projects to your skills and professional growth path. Our consultants work across a wide range of industries and technologies, delivering IT projects both in Poland and internationally. This allows you to build your career in a deliberate way - not by chance.

We are part of an international organization listed on Nasdaq Stockholm, operating in 11 countries. In Poland, we operate with full autonomy. We choose our technologies, processes, and ways of working while maintaining the highest professional standards.

Join us today.

Key areas of the role:

• Backend and APIs - Preparing mocks, designing and adjusting APIs in Java/Kotlin within a microservices architecture, enabling integrations with external strategic partners

• Frontend in React - Building responsive web components, checkout funnels and registration paths, and integrating the frontend with the backend and the mobile app

• Building new services - Working on services that run outside the core market but are integrated with platform services (payments, login, search), delivering fast with the support of AI and agentic development tools

Your responsibilities:

• Designing and adjusting backend APIs and preparing backend mocks using Java or Kotlin within a microservices architecture.

• Developing responsive web components, checkout funnels, and registration pathways using React, JavaScript, HTML, and CSS.

• Integrating systems and endpoints to facilitate onboarding and seamless collaboration with strategic external partners.

• Switching context dynamically between backend enablement and web frontend development depending on project priorities.

• Leveraging AI coding tools and agentic development workflows to accelerate product delivery and streamline full-stack tasks.

Requirements:

• 5+ years of experience in Java or Kotlin and comfortable working with microservices architecture.

• Hands-on frontend experience using React, JavaScript, HTML, and CSS.

• Understanding of REST API principles, JSON data manipulation, and consuming backend endpoints.

• Openness to utilizing AI tools and LLMs in daily development and code generation workflows.

• Proficiency in English at a minimum B2+ level.

• Must reside in and/or have work authorization in Poland.

What we offer

• Work in a Scandinavian culture built on logic, trust, and open dialogue.

• Health and sports benefits tailored to your needs.

• Speed Coaching – short sessions designed to provide new perspectives and solutions.

• Sports training, an internal team, and opportunities to take part in competitions.