Speedup Execution needs to be done for hybrid framework. anu suggestions on how it can be done

You've basically described the general outline of many different framework development structures.  I do something very similar using CSV files (I prefer CSV over Excel because the file format is more portable...but the concept is the same).  

HOWEVER.... without knowing the specifics of the code that you're running with your various drivers and excel file reads, how you're making the decisions for executing keywords, etc...  Really can't give you much directed help.

One thing that I did in my framework about a year ago... I used to drive the keywords with a switch statement (mine was written in JavaScript).  The more keywords I added, the bigger the switch statement got... and I started seeing performance degredation.  So... what I ended up doing is using a data reflection technique where the data that said, "Execute Keyword X" would pass that keyword to a routine that would instantiate a class named "X" and call an "execute" method on that class.  This removed my massive switch statement and sped up my code.  The back end became a bit more involved with needing to use a script extension to instantiate the classes, etc., but it worked out very well.

Now... this is just a suggestion that worked for me... but it may not apply to you.  Again... without more detail, all we can do is guess.