Senior/Principal Frontend Engineer

Join an innovative project at the intersection of FinTech and AI technologies. We are looking for a Senior/Principal Frontend Engineer to help build scalable, high-performance web applications for modern finance and accounting teams. This is a full-time remote position based in Brazil. We at Sigma Software value engineering excellence, collaboration, and continuous growth. In this role, you will work closely with Product, Design, and Backend teams to create intuitive user experiences and deliver impactful solutions for a global SaaS platform. Why join us? You will have the opportunity to work with modern technologies, contribute to AI-powered product development, and grow in a supportive international environment with flexible work arrangements and professional development opportunities. CUSTOMER Our Customer is a global SaaS company building an AI-native revenue platform for modern finance and accounting teams. The company specializes in subscription management, billing, and revenue operations solutions that help businesses automate financial workflows and optimize recurring revenue processes. Their products support scalable financial operations while maintaining high standards of reliability, compliance, and performance. PROJECT The project focuses on developing and enhancing modern web applications that support core payment processing systems and revenue operations workflows. The team works on scalable frontend solutions integrated with multiple payment gateways and backend APIs, ensuring smooth user experiences, high performance, and operational stability. The platform combines financial technology capabilities with AI-driven functionality to improve usability and automation for finance and accounting teams. Develop and maintain scalable, high-performance frontend applications using React and Next.js Collaborate with Product, Design, and Backend teams to deliver seamless and user-friendly experiences Integrate APIs and backend services into frontend applications Participate in architecture discussions, sprint planning, code reviews, and technical decision-making Ensure responsive design, accessibility, and cross-browser compatibility Contribute to continuous improvement of engineering processes, frontend standards, and product quality Work closely with backend engineers to ensure smooth end-to-end functionality Support performance optimization and frontend scalability initiatives 5+ years of professional software engineering experience with strong focus on frontend development Solid commercial experience with React Experience with Next.js or similar modern frontend frameworks Strong proficiency in TypeScript and JavaScript Experience integrating APIs into web applications Understanding of backend concepts and relational databases such as Postgres Knowledge of responsive design, accessibility, and cross-browser compatibility principles Strong communication and collaboration skills Ability to work independently in distributed teams Upper-Intermediate English level or higher WILL BE A PLUS Experience with Vue or Angular Knowledge of Node.js or NestJS Experience with frontend performance optimization and build tools Experience building AI-powered user experiences Experience integrating AI/LLM services into frontend applications Familiarity with OpenAI, Anthropic, AI SDKs, or prompt-based applications PERSONAL PROFILE Product-oriented mindset Proactive communication style Attention to UI/UX quality Strong ownership and accountability Ability to work in collaborative cross-functional teams