Job Description

About the Role
 

We are looking for an experienced Senior React.js Developer with strong expertise in building high-performance, scalable, and secure web applications. The ideal candidate will have hands-on experience in FinTech, complex payment integrations, real-time applications, third-party API integrations, and modern frontend architecture.

You will work closely with Product, UI/UX, Backend, DevOps, and QA teams to build and maintain customer-facing and back-office applications.
 

Key Responsibilities

• Design, develop, and maintain scalable, high-performance applications using React.js.
• Build reusable, maintainable, and well-tested frontend components and architecture.
• Develop responsive and user-friendly interfaces based on UI/UX designs.
• Integrate frontend applications with REST APIs and third-party services.
• Work with payment providers, wallets, banking, KYC, authentication, and other external integrations.
• Collaborate with backend teams working with Java, C# API-based services.
• Handle real-time application requirements using technologies such as WebSockets or event-driven APIs where required.
• Implement secure frontend practices, including authentication, authorization, token handling, and secure API communication.
• Optimize application performance, loading time, scalability, and browser compatibility.
• Work with Docker-based development and deployment environments.
• Collaborate with DevOps teams on CI/CD pipelines and application deployment.
• Troubleshoot production issues and provide technical solutions.
• Participate in architecture discussions, code reviews, and technical decision-making.
• Mentor junior and mid-level developers and promote frontend development best practices.

Qualifications & Experience

• Frontend

  • 7+ years of professional software development experience, with strong hands-on experience in React.js.
  • Expert knowledge of:
    • React.js
    • JavaScript / TypeScript
    • HTML5 / CSS3
    • Responsive web development
    • Component-based architecture
  • Strong experience with modern React concepts:
    • Hooks
    • Context API
    • State management
    • Custom hooks
    • Performance optimization
    • Lazy loading and code splitting
  • Experience with state management solutions such as Redux, Redux Toolkit, Zustand, or similar.
  • Experience with frontend testing tools such as Jest, React Testing Library, or Playwright.

  Backend & API Integration

  • Good hands-on experience with Node.js.
  • Strong understanding of:
    • RESTful APIs
    • API integration
    • JSON
    • Authentication and authorization
    • JWT / OAuth2
    • Error handling and API security
  • Experience integrating with complex third-party APIs and external platforms.
  • Understanding of backend service architecture and microservices is preferred.

  FinTech Experience

  • Previous experience working in Payments, Banking, FinTech, or similar high-transaction environments.
  • Experience with payment flows such as:
    • Deposits
    • Withdrawals
    • Payment provider integrations
    • Transaction status handling
    • Webhooks and callbacks
  • Understanding of secure transaction processing and customer-facing payment journeys.
  • Experience integrating KYC, AML, payment, wallet, or identity verification services is an advantage.
  • Knowledge of real-time data and transaction status updates is preferred.

Preferred Qualifications

• Experience working with microservices-based platforms.
• Knowledge of Kubernetes or container orchestration.
• Knowledge of AWS, GCP, or Azure.
• Understanding of OWASP and secure web application development.
• Experience building iframe-based or embedded applications is a strong advantage.
• Previous experience working on high-volume transaction or high-traffic platforms.

What We Offer

• Competitive compensation package.
• Flexible and remote-friendly work environment.
• Professional growth and development opportunities.
• Exposure to international projects and teams.
• Collaborative and inclusive company culture.
• Opportunity to work with modern technologies and innovative solutions.

Equal Opportunity Employer

Kairostek is an equal opportunity employer. We celebrate diversity and are committed to creating an inclusive environment for all employees. We welcome applications from qualified candidates regardless of race, ethnicity, gender, age, disability, religion, sexual orientation, or background.

How to Apply

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