We are looking for a highly skilled Senior C# ASP.NET Core Developer to join our client team on a freelance basis. The role focuses on developing and optimizing high‑performance, scalable applications within the Temporary Work and Payroll industry. Responsibilities include mastering advanced C# concepts, leveraging Entity Framework Core, designing efficient PostgreSQL data models, and implementing robust unit tests with xUnit and Moq. The ideal candidate will bring strong analytical skills, experience with scalable architecture, and a solid understanding of the payroll domain. French language proficiency is required.