Senior Full Stack Developer (C#/.NET Core + React)

I'm looking for an experienced Full Stack Developer with strong .NET Core and React experience to join our development team on an ongoing contract basis. The ideal developer should be comfortable working across both the backend and frontend, building and maintaining production applications, developing APIs, implementing business logic, and creating responsive React interfaces. We are looking for someone who can take ownership of assigned development tasks, work independently, understand an existing codebase quickly, and deliver clean, reliable, production-ready code. What You'll Work On * Develop and maintain backend services using C# and .NET Core / ASP.NET Core * Design and develop RESTful APIs * Build frontend features using React and TypeScript * Connect React applications with .NET Core APIs * Implement business logic and application workflows * Work with SQL Server and relational databases * Integrate third-party APIs and external services * Debug and resolve frontend and backend issues * Improve application performance and reliability * Refactor and enhance existing functionality * Participate in code reviews and technical discussions * Develop new features from technical requirements * Maintain and improve existing production applications Required Skills Strong hands on experience with: * C# * .NET Core / ASP.NET Core * React * TypeScript / JavaScript * REST APIs * SQL Server * Entity Framework Core * Git * Frontend/backend integration * API development and integration * Debugging and troubleshooting The most important requirement is that you are comfortable working on both sides of the application rather than being exclusively a backend or frontend developer. Preferred Experience Experience with the following is a plus: * Microsoft Azure * Azure App Service * Azure Functions * Azure SQL * Cosmos DB * Microservices * Docker * CI/CD * Azure DevOps * Automated testing * Application monitoring and logging * Cloud-based application architecture * Third-party and enterprise integrations What We Are Looking For We are looking for a developer who can: * Understand an existing application and codebase quickly * Work independently on assigned features and technical tasks * Translate requirements into practical technical solutions * Build clean and maintainable code * Troubleshoot problems across both frontend and backend * Communicate clearly with other developers * Identify potential technical issues before they become larger problems * Work comfortably with existing architecture while suggesting improvements when appropriate You should be comfortable taking a feature from API/backend implementation through React frontend integration and final testing. Experience Level We are primarily looking for a Senior level developer with several years of professional experience building real world web applications. Strong practical experience is more important than certifications. You should be able to work with an existing application, understand how the different components interact, and begin contributing without requiring extensive step-by-step guidance. Engagement This is an ongoing Upwork contract. The workload may vary depending on project requirements and development priorities. Work will generally be organized around specific features, technical tasks, bug fixes, and development deliverables. The engagement is non-exclusive, and you may work with other clients. To Apply Please send us a proposal describing your relevant NET Core and React experience and include one specific example of a full-stack project you have personally developed or contributed to. We are looking for someone who can become a reliable long term development partner and contribute directly to the product rather than simply completing isolated coding tasks.