Senior Java Developer

Senior Java DeveloperLocation: Kraków, Poland (hybrid – 2 days/week from office)Contract type: B2BRate: 140–150 PLN/hProject type: Long-term, enterprise, payments domainAbout the projectFor one of our global financial clients operating in the payments domain, we are building a new engineering team responsible for delivering a Future State Architecture for payment processing.The project focuses on creating a lean, reusable payment processing engine that will become the foundation of next-generation payment capabilities. The work is performed in an inner-sourcing model, with a strong emphasis on reuse, modernization, cloud adoption, and high engineering standards, enabling faster delivery of new product features at scale.Key ResponsibilitiesDeliver engineering expertise for future-state payment architecture and next-generation payment processing capabilitiesDesign, build, and maintain highly available, resilient, and scalable backend servicesProduce high-quality, well-tested code and ensure all quality gates are exceededSupport the transformation and modernization of the existing payment landscape with strong cloud focusActively participate in a wider delivery team contributing to new platform capabilitiesResolve architectural and development blockers and provide hands-on technical guidanceCollaborate closely with DevOps teams to enable CI/CD pipelines and DevSecOps practicesKey AccountabilitiesSet engineering standards and lead by example within the teamAct as a technical expert, identifying process improvements and preventing systemic issuesProvide technical solutions to complex business and architectural problemsDrive architectural decisions aligned with global standards and business strategyMaintain awareness of regulatory, security, and data privacy requirementsDesign, implement, review, and optimize systems for performance, resilience, and operational integrityMentor and coach engineers, supporting their technical and professional growthRequired Qualifications & ExperienceBachelor’s degree in Computer Science, Engineering, or a related field8+ years of experience as an API EngineerStrong experience in API design and architectural documentation (LLDs, gap analysis, data models)5+ years of backend microservices development, application security, authentication, caching, and middleware8+ years of Java experience (Go and/or Rust is a strong plus)Expertise in distributed systems, Spring Boot, microservices architectureExperience with Kafka, Docker, Kubernetes, service meshStrong JVM tuning and performance optimization skillsExperience with observability and monitoring tools (Grafana, Prometheus, Splunk, Jaeger, OpenTelemetry, etc.)Cloud & DevOps experience, including networking (VPC), IAM, sizing, and cost optimizationSolid understanding of Linux, networking, storage, load balancing, and Kubernetes CNISQL knowledge is a strong plusExperience in financial institutions or payment systems is highly desirableExcellent English communication skillsNice to HaveExperience with Go or RustStrong background in payments or large-scale financial systemsPassion for mentoring, coaching, and technical leadershipBenefitsPrivate medical care (Medicover)Sports card (Multisport or equivalent)Life insuranceLong-term cooperation on a stable, enterprise-scale projectAccess to modern technologies and large-scale distributed systemsReal influence on architecture and technical direction