Senior React Developer (Java Backend)

Quick Facts

• Role: Senior React Developer (Java Backend)
• Work model: Hybrid (3 days per week from the office)
• Location: Krakow
• Contract: B2B
• Domain: Financial services

Description

Senior React Developer with Java backend experience for an international financial-services project. You will focus on designing and building high-quality, scalable, responsive, high-performance web applications using React and TypeScript, while also contributing to Java/Spring Boot backend services and REST API integration when needed.

Responsibilities

Frontend (80%)

• Design, develop, and maintain modern web applications using React, TypeScript, and JavaScript.
• Create reusable, modular, scalable, high-performance UI components.
• Build responsive and accessible interfaces with HTML5 and CSS3.
• Implement state management, data fetching, and API integration strategies.
• Develop data-intensive and interactive UIs for large datasets and real-time updates.
• Optimize performance, rendering efficiency, responsiveness, and browser compatibility.
• Write clean, maintainable, testable, well-documented code; participate in code reviews.
• Build automated tests (unit, integration, end-to-end).
• Collaborate with UX/UI designers, product owners, and stakeholders to turn requirements into user experiences.

Backend (20%)

• Develop and enhance backend services using Java and Spring Boot.
• Design, consume, and integrate RESTful APIs and microservices.
• Collaborate on API contracts, data models, and service integration patterns.
• Troubleshoot and optimize across frontend and backend.
• Contribute to backend unit and integration tests.
• Work with event-driven architectures and asynchronous/distributed systems where applicable.

Requirements

• Strong commercial React + TypeScript experience.
• Excellent knowledge of JavaScript (ES6+), HTML5, and CSS3.
• Experience with React Hooks, component composition, and frontend architecture.
• Practical state management experience (e.g., Redux Toolkit, Zustand, or Context API).
• Experience integrating with RESTful APIs and handling asynchronous flows and API errors.
• Expertise in responsive design, accessibility, browser compatibility, and frontend performance optimization.
• Good working experience with Java and Spring Boot.
• Understanding of REST API development (HTTP/JSON) and API integration.
• Familiarity with microservices architecture and service communication.
• Knowledge of JUnit and Mockito.
• Understanding of relational databases and SQL.
• Experience with Git and collaborative development workflows.
• Agile experience, CI/CD familiarity, code reviews, and automated testing.
• Docker and cloud experience is an advantage; Azure is beneficial.

Benefits

• International banking and financial services project.
• Competitive B2B rate.
• Long-term cooperation opportunity.
• Collaboration with an experienced international team.