[dev] Get Tickets consuming too much time when loaded for 500 users

Hi , I am trying to do a load testing on my application which is using OTRS Helpdesk I am using nph-generic ticket connector to get tickets When I am doing a load testing for 500 concurrent users, the response times are very high reaching 20-30 seconds. I tried increasing threads of apache, but that worked to very less extent. Any help is appreciated. Thanks, Jignesh