Does emacs cache something on windows when invoking call-process?

[Eighty Megabytes]

I have the same search command line which is practically instantaneous in the 
windows command prompt, but it takes several seconds when executed via 
call-process.

So I try it in the command prompt, it's instantaneous.

Then I try the same command line from emacs via call-process and it takes 
several seconds.

Subsequent calls via call-process are instantaneous until I don't use the 
feature for a while. Then the next invocation from emacs becomes slow again.

So this behavior raises 2 questions:

1. Why is the same command much slower when invoked via call-process?

2. What does that first call-process call does/caches in emacs which makes 
subsequent calls quick until it forgets something and it's slow again?