Senior .NET Developer Needed for a Production Issue

We are a software development company working on an existing application for one of our clients. We are currently stuck on a specific issue in the client's ASP.NET Core / .NET application and are looking for an experienced developer who can help us identify the root cause and implement a fix. The Issue We have an existing ASP.NET Core Web API application connected to SQL Server. The application works correctly under normal conditions, but sometimes all operations get slow in the production environment, and sometimes new users are unable to even log in. We have already investigated the application and tried several approaches, but we have not been able to identify the exact root cause. We are looking for someone who can: - Review the existing .NET code and understand the relevant flow - Analyze the API request/response behavior - Review logs and exception details - Investigate the database interaction - Identify the root cause rather than simply applying a workaround - Implement and test the fix - Explain what was causing the issue and why the solution resolves it