Fullstack Engineer (Frontend focused)

Rate: 90 – 120 PLN/hour (B2B) We are looking for a skilled Fullstack Engineer (Frontend focused) for service agreement collaboration (B2B contract) to cooperate with a team dedicated to Network Planning at FlixTrain - building internal tools that help plan the timetable and vehicle allocation, reduce manual processes, and increase productivity. This is a greenfield environment with plenty of room to shape new products from the ground up and explore innovative solutions for our internal users. Scope of Services You will independently develop and deliver high-quality frontend features, with occasional backend work, within a self-organized, cross-functional, distributed team. This includes building intuitive user interfaces with a focus on the experience of our internal users. You will also help drive frontend architecture decisions and contribute to technical quality across teams through code reviews and close collaboration. About the Engagement Design and build internal web applications that automate and simplify FlixTrain Network Planning workflows Develop modern, responsive user interfaces with React and TypeScript and contribute to a consistent, reusable frontend architecture Design and implement backend functionality, including GraphQL APIs, server-side logic and database models Work with internal users and stakeholders to understand their needs and turn them into practical product solutions Write and maintain automated tests, to ensure reliability and maintainability Collaborate with other engineers across a distributed architecture within an Agile environment Document technical decisions, solutions and ways of working About You Must have: Hands-on experience with React (React 19 in our stack) and TypeScript, with a strong command of HTML and CSS Experience with an object-oriented backend language. Java is not required, but preferable: Node.js or similar is acceptable, provided you have real backend development experience, not just scripting Hands-on experience in backend web application development: building and designing GraphQL APIs, server-side logic and database design Experience writing tests and working with test runners such as Vitest Understanding of event-driven systems and how to work with them Solid written and spoken English skills Experience working in an Agile setup Curiosity about the business domain. Interest in transportation, logistics or similarly complex domains is a good signal, as is the ability to explain such a domain clearly Nice to have: GraphQL: used in our stack (Spring for GraphQL, Apollo, gql.tada) Java and Spring Boot / Spring Framework Kafka Experience with agentic or AI-assisted coding Collaboration Model Contract type: Cooperation based on a service agreement (B2B/freelance contract), not an employment contract Working model: Independent contractor responsible for delivering agreed services and submitting invoices Location: Open for contractors based in Poland