Java Engineer

Rate: 89 – 119 PLN/hour (B2B) We are looking for a skilled Java Engineer 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 design, develop and deliver reliable backend services within a self-organized, cross-functional, distributed team. This includes building robust APIs and event-driven integrations for our internal tools, with a strong focus on internal user needs. You will also help drive backend architecture decisions and contribute to technical quality across teams through code reviews and close collaboration. About the Engagement Design, build and maintain backend services and APIs that automate and simplify FlixTrain Network Planning workflows Develop and evolve data models and integrations, including asynchronous, event-driven communication between services Work with internal users, product and other engineers to understand their needs and turn them into practical technical solutions Write and maintain automated tests to ensure the reliability and maintainability of the services you deliver Collaborate with other engineers across a distributed architecture within an Agile environment Document technical decisions, solutions and ways of working Our backend stack: Java with Spring Boot AWS Kafka Kubernetes Terraform for IaC GraphQL PostgreSQL GitLab CI About You You have 3 to 5 years of experience building backend applications, from which a couple of years building backend applications in Java or another JVM language such as Kotlin You have worked in cloud environments (ideally AWS) You have practical experience with at least one of the following: Building and running on AWS Designing, building and maintaining event-driven systems with Kafka Deploying and operating workloads on Kubernetes Managing infrastructure as code, ideally with Terraform You write automated tests as a natural part of your development process and care about code quality and maintainability 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 Experience building services with Spring Boot Experience working with databases, relational and/or NoSQL Experience with CI/CD pipelines (GitLab CI or GitHub Actions) A DevOps mindset: you are willing to own pipelines, infrastructure and quality, not just the application code Experience with agentic or AI-assisted coding