Senior Backend Developer (Java / .NET)

Backend Developer (Java or .NET)Location: Warsaw (Hybrid - 3 days per week in the office)Start Date: ASAP / FlexibleCooperation Model: B2B via ExperisWe are looking for an experienced Backend Developer to join an international team building and maintaining scalable backend services and APIs powering client-facing portal applications.ResponsibilitiesDevelop and maintain backend services and REST APIs using Java (Spring Boot) or .NET Core.Design and integrate solutions with relational and NoSQL databases.Collaborate closely with frontend teams to deliver seamless integrations.Build and deploy applications in containerized environments using Docker, Kubernetes, or OpenShift.Implement secure coding practices, automated testing, and CI/CD pipelines.Optimize application performance, scalability, and reliability.Troubleshoot production issues and support application stability.Participate in Agile ceremonies and technical design discussions.Requirements8+ years of backend development experience.Strong expertise in Java or .NET.Hands-on experience building and consuming REST APIs.Experience with Docker, Kubernetes, or OpenShift.Solid SQL and database knowledge.Experience with CI/CD pipelines and automated testing.Strong communication and teamwork skills.Nice to HaveExperience with Kafka, MQ, or other messaging technologies.Cloud-native development experience.Background in financial services, fund administration, or transfer agency environments.What We OfferB2B contract via ExperisHybrid work model (Warsaw, 3 days per week in the office)Long-term international projectsMedicover healthcare packageMultisport cardGroup life insurance