We are looking for a highly skilled Senior C# ASP.NET Core Developer to join our client’s team on a long‑term freelance contract. The role focuses on building high‑performance, scalable applications in the payroll and temporary work sector, leveraging modern .NET technologies, PostgreSQL, and robust unit testing practices. Candidates must be proficient in asynchronous programming, design patterns, and performance tuning, with strong analytical skills and the ability to work independently. French language proficiency is required.