@siva-anantha , We are working on some migration project where some core business logics are in c# code as exe. We have 2 options either rewrite the code into pyspark or use the exe as it is. Since we have a very limited timeline, we are thinking of calling the exe as it is from notebook. Please find my response inline below. 

1) purpose of .exe - what it does?

some core business logics like some calculations, filtering and brand scanning all happens in the exe
2) whether you need Spark parallelism

Not very sure as we have not gone through the code fully.