Descripción del empleo: **Position:** Senior Web Front\-End Engineer **Location:** Remote from Argentina or Brazil only (Full\-time, Contractor) We are seeking a highly skilled **Senior Web Front\-End Engineer** to join our global team. You will play a key role in developing and enhancing a sophisticated web application that supports complex global monetary transactions. The ideal candidate combines expertise in modern front\-end technologies with solid understanding of backend integration, testing, and debugging. This is a long\-term opportunity to work in an international environment, contribute across the full stack, and ensure the performance and reliability of a mission\-critical platform. **Responsibilities:** * Develop, enhance, and maintain a high\-performance web application built with React. * Debug and trace issues in both the browser and application logs. * Collaborate with engineers, QA, and release managers for smooth delivery cycles. * Contribute to backend integration using Node.js and Express. * Design and implement testing strategies with Jest and React Testing Library. * Utilize Apollo GraphQL for data fetching and state management. * Participate in code reviews and mentor junior engineers. * Ensure cross\-browser compatibility and responsive design. * Work in an agile environment with Jira and CI/CD pipelines in Jenkins. **Requirements – Must Have:** * Expert\-level **JavaScript (ES6\+)** with strong coding practices. * Deep experience in **React** (hooks, context API, state management, performance optimization). * Strong knowledge of **Node.js** and **Express.js** for backend integration. * Proficiency with **Jest** and **React Testing Library**. * Familiarity with **Apollo GraphQL**. * Excellent debugging skills with browser developer tools. * Advanced English (B2\+/C1\) for daily communication in global teams. **Nice to Have:** * Broader GraphQL knowledge (schema design, server\-side implementation). * Experience with **Cypress** or other E2E frameworks. * Familiarity with **Jenkins** and agile project management tools such as Jira. * Strong **CSS/SASS** skills and knowledge of cross\-browser compatibility issues. **What We Offer:** * 100% remote, full\-time contractor role. * Long\-term engagement in global projects. * Multicultural, collaborative work environment. * Opportunities for career growth and continuous learning.