We’re looking for a skilled and proactive Senior Full Stack Developer with strong expertise in Java and React to join our engineering team. In this role, you'll take part in designing and building scalable web applications end to end - from robust backend services to modern, responsive frontends.Responsibilities:Provide technical expertise and guidance to the engineering team, including conducting code reviews, and fostering a culture of excellence in software development practicesWrite high-quality, maintainable code for critical components, features, or modules of the software application, while also contributing to the overall codebase and enforcing coding standards and best practicesAnalyze and solve complex technical problems, including performance bottlenecks, scalability challenges, and system failures, through systematic debugging, root cause analysis, and collaboration with cross-functional teamsRefactoring and improving existing codebase to enhance maintainability, extensibility, and readability, while also identifying and addressing technical debt and legacy code issuesCreate and maintain technical documentation, including design documents, architecture diagrams, and best practices guides, to facilitate knowledge sharing, onboarding, and collaboration within the teamEnsure the overall quality and reliability of software products through rigorous testing practices, including unit tests, integration tests, and end-to-end tests, as well as promoting a culture of testing and quality assurance within the teamMin requirements:2–3 days per week from the Warsaw officeStrong knowledge and hands-on experience in backend development with Java & Spring BootDeep understanding of RESTful web services and microservices architectureExpertise in API development (designing interactions between platform components)Ability to develop frontend applications using JavaScript, HTML, CSS, ReactExperience in user interface (UI) designProficiency in writing maintainable code following TDD/BDD paradigmsSolid grasp of Clean Code principles: SOLID, KISS, DRY, Clean ArchitectureStrong experience with containerization & orchestration (Docker, Kubernetes)Hands-on experience with application development lifecycle and CI/CD pipelinesPractical knowledge of authentication and authorization methodsPractical experience with secure connectivity (mTLS, Message Level Encryption, etc.)Would be a plus:Kotlin experience or willingness to learnKnowledge of encryption/decryption methods and tools, including HSMs (Hardware Security Modules)Broader experience with enterprise-level security integrationsWe offer:Opportunity to work on bleeding-edge projectsWork with a highly motivated and dedicated teamCompetitive salaryFlexible scheduleBenefits package - medical insurance, sportsCorporate social eventsProfessional development opportunitiesWell-equipped officeAbout us:Grid Dynamics (NASDAQ: GDYN) is a leading provider of technology consulting, platform and product engineering, AI, and advanced analytics services. Fusing technical vision with business acumen, we solve the most pressing technical challenges and enable positive business outcomes for enterprise companies undergoing business transformation. A key differentiator for Grid Dynamics is our 8 years of experience and leadership in enterprise AI, supported by profound expertise and ongoing investment in data, analytics, cloud & DevOps, application modernization and customer experience. Founded in 2006, Grid Dynamics is headquartered in Silicon Valley with offices across the Americas, Europe, and India.