[Job-27786] Senior FullStack Developer .NET & React at CI&T

Somos especialistas em transformação tecnológica, unindo expertise humana à IA para criar soluções tech escaláveis. Com mais de 8,000 CI&Ters ao redor do mundo, já formamos parcerias com mais de 1,000 clientes durante nossos 30 anos de história. Inteligência Artificial é nossa realidade. Importante: se você reside na Região Metropolitana de Campinas, sua presença nos escritórios da cidade será obrigatória, conforme a política de frequencia vigente. Description ABOUT THE ROLE At 3Degrees, we are transitioning from legacy proprietary systems to an AI-first, enterprise-grade technology platform. We are looking for a Full Stack Engineer to lead the automation of our Receipts Management process, a mission-critical initiative involving the migration of legacy data to ION’s Carbon Zero platform. You will be a founding member of an agile unit dedicated to decommissioning 17-year-old systems and replacing them with high-performance, integrated solutions. In this role, you will collaborate with our US-based teams to build "Callisto," our internal data management platform, ensuring straight-through processing (STP) for environmental commodities. This is a high-impact opportunity to apply modern engineering standards and AI-assisted development to solve complex climate tech challenges at startup velocity. WHAT YOU'LL DO Legacy Migration & Integration: Lead the transition of core trading functions from Legacy application to the ION’s Carbon Zero platform, focusing on receipt processing automation across ~40 global registries. Full Stack Development: Build and maintain the Callisto UI using React and TypeScript, while developing robust back-end business logic and APIs in C#/.NET Core or Python. Registry Automation: Develop and support integrations with external EAC (Environmental Attribute Certificates) tracking systems via APIs or AI-enabled RPA functionality. AI-First Execution: Actively use AI-assisted coding tools (e.g., Cursor, Claude Code, GitHub Copilot) to accelerate development speed and maintain high code quality. Cross-Functional Collaboration: Partner with US-based technical leads and business stakeholders to map integration touchpoints across Salesforce, NetSuite, and our operational databases. ABOUT YOU You are a versatile builder who thrives in a fast-paced, "AI-First" engineering environment. You possess a strong balance of frontend craft and backend rigor, with a specific interest in environmental markets and decarbonization. You are comfortable navigating legacy architectures while architecting modern, scalable alternatives that leverage automated workflows. 8+ years of experience in C#/.NET/Python development and React/TypeScript frontend design. Advanced database skills (Azure SQL, Managed Instances) with the ability to analyze and optimize complex schemas. Professional-level English proficiency (C1+) with the ability to communicate complex technical decisions to US-based stakeholders. A "product mindset" with the ability to move from prototype to production in 6–8 week cycles. Availability to maintain high overlap (at least 6 hours) with US Pacific Time (PT) working hours. Demonstrated experience using AI tools (LLMs, agentic frameworks) to accelerate your personal development workflow. HOW WE DEFINE SUCCESS Within the first 30 days: Gain a firm grasp of the "Callisto" architecture, the ION Carbon Zero roadmap, and the specific data structures within the legacy SQL trading environment. Build strong cross-functional relationships with US-based technical leads and understand the agile unit's communication and deployment cadences. Successfully clear 3-5 initial feature/bug tickets to demonstrate proficiency in the tech stack and AI-assisted development tools. Within the first 90 days: Hone development skills within the environment to contribute to the Receipts Management SOW in a meaningful way, delivering the first set of automated registry integrations. Establish a consistent high-velocity coding loop using AI-assisted tools (Cursor/Claude/Copilot), ensuring all contributions meet documented security and documentation standards. Actively participate in the Discovery process for North American registry integrations, helping to map technical debt and architectural requirements. Within the first 6 months: Contribute independently as a senior developer, co-leading the technical execution of the North American registry integration phase. Help the team meet department goals by delivering production-ready APIs and UI components that reduce manual processing time for the trading team. Demonstrate a firm grasp of the end-to-end SDLC by independently managing complex project slices from prototype to MVP. Within 1 year: Demonstrate success across all automation goals, achieving 90%+ straight-through processing for targeted registry transfers and retirements. Successfully decommission legacy components for the receipts process, migrating all core functionality to a stable, integrated enterprise platform. Serve as a mentor for the engineering team on AI-first development best practices, driving continuous improvement in delivery speed and code reliability. Nossos benefícios: - Plano de saúde e odontológico; - Vale alimentação e refeição; - Auxílio-creche; - Licença parental estendida; - Parceria com academias e profissionais de saúde e bem-estar via Wellhub (Gympass)  TotalPass; - Participação nos Lucros e Resultados (PLR); - Seguro de Vida; - Plataforma de aprendizagem contínua (CI&T University); - Clube de descontos; - Plataforma online gratuita dedicada à promoção da saúde física, mental e bem-estar; - Curso gestante e parentalidade responsável; - Parceria com plataformas de cursos online; - Plataforma para aprendizagem de idiomas; - E muitos outros Mais detalhes sobre os nossos benefícios aqui: [Upgrade to PRO to see link] Na CI&T, a inclusão começa no primeiro contato. Se você é pessoa com deficiência, é importante apresentar o seu laudo durante o processo seletivo. Consulte quais dados são necessários conter no laudo clicando aqui. Assim, podemos garantir o suporte e as adaptações que você merece. Se ainda não tem o laudo caracterizador, não se preocupe: podemos te apoiar para obtê-lo. Temos um time dedicado de Saúde e Bem-estar, especialistas em inclusão e grupos de afinidade que estarão com você em todas as etapas. Conte com a gente para fazer essa jornada lado a lado.