Experienced Debugger for financial real time screener (.NET server-client) needed

Hej guys, I have contracted a programmer, that has written a stock screener for me. It is a server client system. Everything is written in .NET. Stock prices are streamed from an api based on a c# dll. For the Frontend ag-grid is used and data is send and received via SignalR. Even though CPU usage is around 20% and Ram is about 800 MB, the screener lags updating once the US markets start for at least 20 seconds. But the purposes of the screener is to compare different stock exchanges with each other in real time. We need somebody really experienced in writing .net real time applications for stock exchanges. We believe that pushing the results from our backend to Frontend is our bottleneck. The contractor I am searching has also huge experience with real time pushing to front end.