I have fear that sufficient increase in number of postgres.exe after one or two logins on servers may down the speed of the server or even server. Is there any solution or technique to overcome this overhead.
Did you test this?
What OS are you using?
With PostgreSQL every connection gets a process, processes can be reused, so unless you have a very low spec system, that should not be a problem.
PostgreSQL is designed as a client/server architecture, which requires separate processes for each client and server, and various helper processes. Many embedded architectures can support such requirements. However, if your embedded architecture requires the database server to run inside the application process, you cannot use Postgres and should select a lighter-weight database solution.
I could not find the reason as to why this way has been chosen by the developers