Empresa: Kstack
Location: São Paulo, Brazil — Hybrid Job Description We are seeking a highly skilled and experienced Senior UI Developer with a strong background in React.js, Next.js, NestJS, TypeScript, and unit testing . The ideal candidate has a proven track record of building scalable, responsive, and high-performance web applications. This role requires a collaborative mindset, strong attention to detail, and the ability to take ownership of UI development initiatives from concept through implementation. Key Responsibilities • Design, develop, and maintain modern, scalable front-end applications using React.js and NestJS . • Write clean, efficient, maintainable, and well-documented code using TypeScript . • Implement and maintain unit tests using frameworks such as Jest and React Testing Library to ensure code quality and reliability. • Optimize applications for performance, scalability, responsiveness, and overall user experience . • Partner closely with UX/UI designers, back-end developers, and Product Owners to deliver seamless user experiences. • Mentor junior developers and review their work to ensure adherence to engineering best practices and coding standards. • Participate actively in code reviews, architectural discussions, and Agile ceremonies , including sprint planning and retrospectives. • Stay current with front-end technologies, frameworks, and industry trends to promote innovation and engineering best practices across the team. Required Skills & Qualifications • 10+ years of overall software development experience. • Strong expertise in React.js and NestJS . • Proficiency in Next.js, TypeScript, and modern JavaScript (ES6+) . • Hands-on experience with unit and automated testing tools and frameworks, such as Jest, Mocha, and Cypress . • Strong understanding of HTML5, CSS3, Sass/SCSS, and responsive web design . • Familiarity with state management libraries such as Redux, Zustand, or Recoil . • Experience integrating applications with RESTful APIs and GraphQL . • Knowledge of CI/CD pipelines and version control platforms such as Git, GitHub, and GitLab . • Excellent problem-solving skills and strong attention to detail. • Strong verbal and written communication skills, with the ability to collaborate effectively across teams. Education • Bachelor’s or Master’s degree in Computer Science, Engineering, or a related field.