Java Developer - B2B Contract, Warsaw, Poland

We are looking for a Java Developer for a B2B contract opportunity, operating in a hybrid model based in Warsaw, to join a specialist engineering team delivering critical changes across complex payment platforms. Role overview: You will work within a small, experienced delivery pod, focusing on analysing and enhancing legacy systems in line with evolving financial messaging requirements. This role requires strong technical depth, the ability to navigate and refactor complex codebases, and confidence working in time-sensitive delivery environments. Technical skills and experience: Strong hands-on experience with Java and the Spring ecosystem (including dependency injection, data access, and security)Proven experience designing and developing RESTful APIs across full stack applicationsSolid knowledge of relational databases (e.g. DB2) and NoSQL databases (e.g. MongoDB), including schema and document modellingExperience working with event-driven and distributed systems, including streaming platforms (e.g. Kafka), producers/consumers, and stateful processingFamiliarity with messaging technologies (e.g. IBM MQ, JMS) and asynchronous communication patternsExperience with build and dependency management tools (e.g. Maven) and multi-module project structuresPractical knowledge of containerisation (e.g. Docker) and modern development environmentsExperience with version control (Git) and CI/CD pipelines (preferably GitLab CI)Exposure to infrastructure as code and environment provisioningUnderstanding of financial systems, payments, or transaction-heavy platforms, including familiarity with financial messaging standards (e.g. ISO 20022, SWIFT)Scripting capability (e.g. Python) to support automation or data processingProven ability to analyse, reverse engineer, and enhance legacy systems with limited documentation What we’re looking for: Strong problem-solving capability and attention to detailConfidence working in complex, fast-paced environments with evolving prioritiesAbility to balance delivery speed with code quality and maintainabilityEffective communication skills and a collaborative mindset within distributed teamsOwnership, accountability, and a proactive approach to improving systems and processes If you’re a developer who enjoys solving complex technical challenges and wants to work on impactful, large-scale systems, we’d be keen to speak. Apply now or reach out directly for a confidential conversation.