FinTech .NET Module Development

Our FinTech web app is moving into the next release, and the spotlight is now on the Bill Payments and User Management modules. I need an expert who can shape these areas end-to-end, ensuring they perform smoothly, scale cleanly, and stay rock-solid secure... (Budget: ₹750 - ₹1250 INR, Jobs: .NET, .NET Core, API, ASP.NET, ASP.NET MVC, C# Programming, Microsoft SQL Server, React.js)