FullStack Developer Trainee

We are seeking a FullStack Developer Trainee position based in our Poznań Office.

Ready to help build a better future for generations to come

In an ever-changing fast paced world we owe it to ourselves and our future generations to live life responsibly. At ROCKWOOL we work relentlessly to enrich modern living through our innovative stone wool solutions.

Join us and make a difference!

About the role

Were building the next generation of AI-powered applications at ROCKWOOL and were looking for aFullStack Developer Traineewho wants to work across the entire stack: from React components in the browser to APIs and data on the backend.

This is a trainee position but you will not be limited to small fixes only. Youll work with a modern web stack (React on the frontend services on the backend - depending on the specific product) and help us design and build features that actual users rely on every day.

If you enjoy both frontend and backend and you already know the basics of React and server-side development this role will give you the chance to grow quickly.

What you will be doing

You will help design and build both thefrontendandbackendof our internal AI apps.

More specifically you will:

• BuildReactcomponents pages and flows for chat interfaces configuration screens dashboards and admin tools
• Implement or extendbackend APIs(REST/GraphQL) inPythonto support new features and data flows
• Work withAI-related services(e.g. LLM endpoints prompt & response handling logging and analytics)
• Design and wiredata modelsand persistence (e.g. relational or NoSQL databases)
• Take part in code reviews grooming and design discussions with experienced engineers
• Learn how to shipproduction-qualityfeatures end-to-end: from idea implementation deployment monitoring

Youll be guided by senior engineers but youll also own real tasks and see your work in production.

Tech stack youll touch

The exact stack can vary by product but you can expect something like:

Frontend:

• React (functional components hooks)
• JavaScript/TypeScript
• HTML5 CSS3 (Flexbox Grid) possibly a utility CSS framework or component library

Backend:

• (Express NestJS or similar) or Python services (FastAPI)
• RESTful APIs possibly GraphQL
• Data persistence: relational DB (SQL)
• Integration withAI services(LLM endpoints via HTTP/SDKs)

Tooling & DevOps:

• Git GitHub/GitLab Pull Requests and code reviews
• Package managers (npm/yarn/pnpm)
• Basic CI/CD pipelines (build test deploy)
• Containerization (Docker) and cloud platforms (e.g. Azure) exposure not expert level

You dont need to know all of this today but you should be hungry to learn it.

What youll learn with us

During your traineeship youll learn how to:

• Work in ashared codebasewith multiple developers and clear standards
• Design and implementfull user flows: UI API database and integrations
• Buildinterfaces for AI: conversational UIs prompt builders history views monitoring screens
• Make trade-offs betweenperformance readability and complexity
• UseAI as a development accelerator(for scaffolding code refactoring tests documentation)
• Contribute to ourengineering practices: code review testing documentation and deployment

By the end of the traineeship our goal is that youre ready for ajunior fullstackrole (or to specialize in frontend/backend if you prefer).

What you bring

This is a trainee role but we do expect asolid technical foundation.

Frontend basics:

• Good understanding ofJavaScript(ES6): promises async/await arrow functions array methods
• BasicReact:
  • Functional components and props
  • Hooks like useState and useEffect
  • Simple state & event handling
• SolidHTML & CSSfundamentals and basic responsive design

Backend basics:

• Experience building at least asimple API(for example or ideally Python)
• Understanding ofHTTPconcepts (methods status codes headers)
• Basics ofrouting controllers request/response handling
• Very basic knowledge ofdatabases:
  • CRUD operations
  • Tables/collections and simple queries

General:

• Comfortable usingGit(branching committing merging pull requests)
• Understanding of how aweb appworks endtoend (browser frontend backend database external APIs)

If you can show a small fullstack project (e.g. React frontend Node/Python API database) onGitHub/GitLab thats a big plus.

Nice-to-have (bonus points not requirements):

• TypeScripton frontend and/or backend
• Experience withReact Routeror similar routing
• Familiarity withORMs/ODMs(e.g. Prisma Entity Framework Mongoose)
• Basicauthentication/authorizationexperience (JWT OAuth etc.)
• Some exposure totesting(Jest Mocha xUnit etc.)
• Interest or experience withAI/ML(using LLM APIs vector databases prompt engineering github copilot cursor claude code etc.)
• Basic understanding ofloggingmonitoring orerror trackingin web apps

You might be a great fit if you:

• Are a student or recent graduate in Computer Science Software Engineering or a related field - or selftaught with strong portfolio projects
• Enjoy working onboth frontend and backend and are curious about how everything fits together
• Learn quickly ask questions and like tofigure things out
• Communicate clearly and enjoy working in ateam environment
• Are genuinely curious aboutAIand excited to build products around it
• Can communicate in English (spoken and written) in a professional context

What we offer

By joining our team you become a part of the people-centric work environment of a Danish company. You will gain valuable experience in one of our teams which will be a good start in your professional life.

Moreover we offer to our interns:

• team building events
• flexible working hours
• an office-first approach: option to work from home

Also you will work in a modern office full of comfort zones and activity places in Crown Square have prepared an onboarding programme for you. This will give you the perfect opportunity to learn the process details and connect with the new team a close-knit group of people who are always ready to help each other out.

It could be a great opportunity to start your professional career with ROCKWOOL!

Ready to apply

If you recognize yourself in this profile and challenge we kindly invite you to apply with CV written in English. If youve built personal academic or hackathon projects that youre proud of and are able to share the code (e.g. on GitHub or GitLab) feel free to include a link to your portfolio or repositories - wed be happy to take a look.

Who we are

We are the world leader in stone wool solutions. Founded in 1937 in Denmark we transform volcanic rock into safe sustainable products that help people and communities thrive. We are a global company with more than 12000 employees located in 40 countries with 51 manufacturing facilities all focused on one common purpose to release the natural power of stone to enrich modern living. Sustainability is central to our business strategy. ROCKWOOL was one of the first companies to commit to actively contributing to the United Nations Sustainable Development Goals (SDGs) framework and are actively committed to 11 SDGs including SDG 14 Life Below Water. Through our partnership with the One Ocean Foundation and in connection with our sponsorship of the Denmark SailGP team we will help raise awareness around ocean health challenges in an effort to accelerate solutions to protect it.

Diverse and Inclusive Culture

We want all our people to feel valued respected included and heard. We employ 79 different nationalities worldwide and are committed to providing equal opportunities to all employees promote diversity and work against all forms of discrimination among ROCKWOOL employees. At ROCKWOOL you will experience a friendly team environment. Our culture is very important to fact we refer to our culture as The ROCKWOOL Way. This is the foundation in which we operate and is based upon our values of ambition responsibility integrity and efficiency.