Senior Java Developer

Job Description We are looking for Senior Java Developers to join a long-term payments technology programme focused on terminal management systems supporting more than 300,000 payment terminals across multiple hardware vendors. The role combines backend development, integrations, and system modernisation within a complex enterprise payments environment. This is a hands-on Java role working across both legacy and modern architectures, including migration from WildFly-based systems to Spring Boot microservices, with strong focus on integrations, distributed systems, and payment infrastructure reliability. Responsibilities • Design and implement IT solutions based on analytical and technical documentation • Review analytical documentation and translate it into technical implementation • Create and maintain technical documentation • Support technical upgrade and modernisation of the existing system • Work with legacy code and contribute to gradual system migration • Conduct regular application scans and remove vulnerabilities • Build and maintain integrations with internal and external systems • Work with distributed transactions, queues, caching, and database integrations Requirements • Very good knowledge of Java 8+ and object oriented programming • Practical experience with Spring, Spring Boot, Hibernate/JPA, and JEE • Experience designing, implementing, documenting, and testing application components independently • Practical knowledge of RabbitMQ or other message queue systems • Good knowledge of Maven, Git, GitLab, GitLab CI/CD, Jenkins, Nexus, Jira • Knowledge of relational databases, especially Oracle • Practical experience with REST API design • Experience with system integrations and distributed systems • Experience with application servers such as JBoss / WildFly • Knowledge of scanning tools such as Fortify or Sonatype • English B2 • Full availability in the Polish time zone • Ability to work 4 days per week from the Warsaw office Nice to have • Experience in payments, acquiring, terminal management, or financial services • Experience with SOAP, RMI, database links, or direct database integrations • Experience with Hazelcast or distributed caching • Experience with distributed transaction patterns such as two phase commit or Saga • Experience working with legacy systems and migration programmes • Experience with GWT / GWTExt Benefits Solid, competitive salary Work in a multinational environment on international projects Comprehensive healthcare Long-term B2B contract with a stable project pipeline Flexible hybrid model (4 days/ week on-site in Warsaw)