React.js Software Engineer, freelancer

About this role

About Espeo Software

We are a technology company that started its journey in 2008. For more than 17 years, we have been assisting companies in developing and implementing innovative fintech solutions. Leveraging our expertise in areas such as blockchain, online payments, and more, our clients can invent and develop cutting-edge solutions and services that keep them at the forefront of innovation. About the opportunity: You will take ownership of key frontend domains, contribute to architectural decisions, and influence how web applications are built, operated, and continuously improved across multiple products and markets. This position is open to both Mid-Level and Senior Engineers – responsibilities and impact will scale according to experience. Scope of services (applies to both Mid-Level & Senior): Design, build, and maintain high-quality React.js applications within a component-driven architecture Architect and enforce component libraries, state management patterns, and frontend standards across teams Implement performant, accessible UIs that scale across multiple markets and localization requirements Integrate with backend REST APIs and manage async data flows Ensure code quality, performance, accessibility, and comprehensive testing (unit, integration, end-to-end) Collaborate across teams and contribute to platform-wide frontend standards Take ownership of frontend reliability and operability, proactively reducing technical debt Leverage AI-native tools (Copilot, Cursor, Claude) to accelerate delivery and improve code quality Support a “you build it, you run it” mindset Here's a set of skills we require: Middle Level 3-5 years professional software development experience Solid experience with React.js (hooks, functional components) and modern JS/TS Familiarity with state management (Redux, React Query, Context API, or similar) Unit tes