Senior React Developer (Java Backend)

• We are looking for an experienced Senior React Developer (Java Backend) to join an international project in the financial services domain.
• Location: Krakow

Work model: Hybrid - 3 days per week from the office Contract: B2B

About the Role

We are looking for Senior React Developer with Java backend experience who is passionate about building modern, scalable, responsive, and high-performance web applications. The ideal candidate will have strong expertise in React and TypeScript, combined with a solid understanding of Java-based backend services and RESTful API integration.

In this role, you will primarily focus on designing and developing high-quality frontend applications, delivering intuitive user experiences, and collaborating closely with backend engineers, product owners, and business stakeholders. You will also contribute to Java backend development and integration when required.

The role offers an opportunity to work on complex business applications, contribute to architectural decisions, and apply modern engineering practices in an Agile development environment.

Key Responsibilities

Frontend Development - 80%

• Design, develop, and maintain modern web applications using React, TypeScript, and JavaScript.
• Build reusable, modular, scalable, and high-performance UI components following frontend engineering best practices.
• Develop responsive and accessible user interfaces using HTML5, CSS3, and modern styling approaches.
• Implement efficient state management, data fetching, and API integration strategies.
• Build data-intensive and interactive user interfaces capable of handling large datasets and real-time updates.
• Collaborate with UX/UI designers, product owners, and business stakeholders to translate business requirements into intuitive user experiences.
• Optimize application performance, rendering efficiency, responsiveness, and browser compatibility.
• Write clean, maintainable, testable, and well-documented code.
• Develop and maintain automated tests using appropriate unit, integration, and end-to-end testing frameworks.
• Participate in code reviews, technical discussions, and continuous improvement initiatives.

Backend Development - 20%

• Develop, maintain, and enhance backend services using Java and Spring Boot.
• Design, consume, and integrate RESTful APIs and backend microservices.
• Collaborate with backend engineers to define API contracts, data models, and service integration patterns.
• Support troubleshooting, debugging, and performance optimization across frontend and backend components.
• Contribute to unit testing, integration testing, and maintaining the reliability of backend services.
• Understand event-driven architectures, asynchronous communication, and distributed systems where applicable.

Required Skills and Experience

Frontend Technologies

• Strong commercial experience developing applications with React and TypeScript.
• Excellent knowledge of JavaScript, modern ES6+ features, HTML5, and CSS3.
• Experience with React Hooks, component composition, reusable UI patterns, and frontend architecture.
• Practical experience with state management solutions such as Redux Toolkit, Zustand, Context API, or equivalent.
• Experience integrating frontend applications with RESTful APIs.
• Strong understanding of asynchronous programming, API error handling, and data-fetching patterns.
• Experience with responsive design, accessibility, browser compatibility, and frontend performance optimization.
• Understanding of frontend security, maintainability, and scalability best practices.

Java Backend Technologies

• Good working experience with Java and Spring Boot.
• Understanding of REST API development, HTTP protocols, JSON, and API integration.
• Familiarity with microservices architecture and backend service communication.
• Knowledge of Java unit testing frameworks such as JUnit and Mockito.
• Understanding of relational databases and SQL.
• Familiarity with exception handling, logging, debugging, and backend troubleshooting.

Software Engineering and Delivery

• Experience working with Git and collaborative development workflows.
• Understanding of Agile methodologies, CI/CD, code reviews, and automated testing.
• Familiarity with Docker, cloud environments, and deployment pipelines is an advantage.
• Experience with Microsoft Azure or other cloud platforms is beneficial.
• Strong analytical thinking, problem-solving skills, and attention to detail.
• Excellent communication and collaboration skills, with the ability to work effectively with technical and non-technical stakeholders.

Ideal Candidate Profile

The ideal candidate is a frontend-focused engineer with strong React expertise and practical Java backend capabilities.

Should be comfortable taking ownership of frontend features end to end, collaborating with backend teams, integrating APIs, and contributing to Java services when needed.

We value engineers who combine technical excellence with a product-oriented mindset, take pride in delivering high-quality software, and actively contribute to a collaborative engineering culture.

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