December 17, 2025

Java Developer

Mid • Hybrid

Warsaw, Poland

Sii ensures that all employment-related decisions are made solely on the basis of qualifications and competencies. We are committed to equal treatment of all individuals, regardless of any protected characteristics, and promoting a diverse and inclusive work environment.


We are looking for a mid-level Java Developer to join our team. You will work on a modern backend built in Java and Spring Boot, expose RESTful APIs consumed by the frontend, and integrate with multiple external systems. This is a hands-on role where you will take part in building new features, improving system architecture, and ensuring code quality.


Your tasks

  • Develop, maintain, and optimize backend services built with Java and Spring Boot

  • Design and implement REST APIs used by the frontend and external partners

  • Integrate with external APIs and ensure reliable data exchange

  • Write clean, testable, and maintainable code (unit & integration tests with Spock/JUnit)

  • Work with PostgreSQL and use Flyway for database migrations

  • Participate in code reviews and contribute to continuous improvement

  • Collaborate with cross-functional teams in an Agile environment

  • Use Git for version control and GitHub Actions for CI processes


Requirements

  • Minimum 4 years of commercial experience in Java development

  • Strong knowledge of Spring Boot and building REST-based applications

  • Proficiency with SQL and relational databases (PostgreSQL)

  • Experience with unit and integration testing (Spock/JUnit)

  • Solid experience working with Git

  • Practical understanding of API integrations

  • Strong analytical and problem-solving abilities

  • Good command of both English and Polish (written and spoken)

  • Residing in Poland required


Nice-to-have requirements

  • Experience with AWS or other cloud services

  • Familiarity with Docker or containerization practices

  • Knowledge of CI/CD pipelines (e.g., GitHub Actions)

  • Understanding of software architecture and design patterns

  • Previous use of Flyway for schema versioning


What we offer 

  • Great Place to Work since 2015 - it’s thanks to feedback from our workers that we get this special title and constantly implement new ideas 

  • Employment stability - revenue of PLN 2.1BN, no debts, since 2006 on the market 

  • We share the profit with Workers - over PLN 76M has already been allocated for this aim since 2022 

  • Attractive benefits package - private healthcare, benefits cafeteria platform, car discounts and more 

  • Comfortable workplace – class A offices or remote work 

  • Dozens of fascinating projects for prestigious brands from all over the world 

  • PLN 1 000 000 per year for your ideas - with this amount, we support the passions and voluntary actions of our workers 

  • Investment in your growth – meetups, webinars, training platform and technology blog – you choose 

  • Fantastic atmosphere created by all Sii Power People 


Join the Sii team – develop your skills, gain experience, and build your career!