Good day swetaAgarwal,
There are several things you may need to consider improving your Form performance, first thing is the number of rules you are using, the more configured rule on a form the higher the load to process, meaning many rules consume resources more than lesser rules.
Another thing you may need to consider is enabling IIS caching on initial load of a form, there is a documented article on how you can do this, see below shared link ta a relevant KB.
http://help.k2.com/kb001759
The third thing is considering your Server Hardware and Software, for detailed info. on this, follow the below shared link.
http://help.k2.com/kb001858
Lastly, I also think Modifying the hosts file can also have a positive impact to improve performance of your application and the environment itself. See the below shared KB link for a detailed info. regarding this.
http://help.k2.com/kb001678
Also note that these might only be few alternatives amongst many to help improve K2 performance or applications built using K2. I however hope this information will be helpful.
Best regards,
Abraham.