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# Senior Frontend Developer

- **Company:** Zexter
- **Location:** Madrid, Spain (Remote available)
- **Contract:** Permanent contract
- **Skills:** JavaScript (Programming Language), Application Programming Interfaces (APIs), Software Quality, Code Review, Continuous Integration, Cross-Origin Resource Sharing (Ajax Programming), Middleware, Github, Web Browsers, Routing, Node.Js, Role-Based Access Control, Coupa Supplier Portal, Next.js, Web Application Security, TypeScript, WebSocket, Web Usability, Eslint, Data Logging, Network Routers, Integrated Service Routers, Tailwind, ReactJS, Cypress (Programming Language), Caching, Cross-Site Scripting (XSS), Backend, Git, Gitlab-ci, Playwright, Sentry, Real Time Data, Front End Software Development, React Testing Library, JestJS, Api Management, Docker, Monolithic Repository
- **Published:** September 17, 2026
- **Apply:** https://www.indeed.com/viewjob?jk=9dc93595a13a2f97

## About the Role

We are now looking for a Senior Frontend Developer to help us build and scale our in-house platform. This is a hands-on, product-focused role for someone with strong React and TypeScript expertise, solid experience building production-grade applications, and the ability to take ownership of frontend development in a growing product., * 5+ years of commercial frontend development, including 3+ years with React, with experience owning and supporting production applications under real user load.

 * Strong TypeScript skills: strict mode, generics, utility types, discriminated unions, and fully typed API contracts without any.
 * Advanced React 18/19 & Next.js knowledge: hooks, render cycle, Suspense, Server/Client Components, App Router, SSR/SSG/ISR, middleware, caching and routing.
 * Experience with TanStack Query, including query management, invalidation, SSR prefetching/hydration, persistent cache and optimistic updates.
 * Ability to design and evolve large-scale frontend architecture: clear module boundaries, layered structure, public APIs, and gradual legacy migration without blocking feature development.
 * Strong focus on code quality and testing: Vitest/Jest, React Testing Library, Playwright/Cypress, ESLint/Prettier, code reviews and Core Web Vitals optimization.
 * Experience with modern frontend infrastructure and operations: Git, CI/CD (GitHub Actions/GitLab CI), Sentry, Docker and Node.js deployments.
 * Solid understanding of API communication and web security: REST, WebSocket, authentication/refresh flows, CORS, CSP, XSS, SSRF and secure BFF patterns.
 * Experience working in a cross-functional product team with backend, design and QA, plus hands-on knowledge of Tailwind CSS, Zod and internationalization (next-intl or equivalent)., * Experience in iGaming, betting, fintech or other high-load domains with real-time data.
 * Experience with admin panels and role-based access control.
 * Node.js at the level of writing a BFF layer, proxies and small services.
 * Monorepo experience: pnpm workspaces, Turborepo, Nx.
 * Experience supporting legacy browsers and polyfills on a modern stack.
 * Experience setting up observability: logging, tracing, dashboards.

## Description

* Develop and maintain scalable, high-performance frontend applications using React, Next.js and TypeScript.
 * Design and implement robust frontend solutions, contributing to architecture decisions and improving existing systems.
 * Build and deliver end-to-end product features, collaborating closely with backend developers, QA, design and product.
 * Ensure code quality, performance and reliability through testing, code reviews, monitoring and continuous optimization.
 * Contribute to development processes and frontend best practices, improving tooling, CI/CD, observability and overall engineering quality.