Traditional web applications are getting modernized to meet the expectations of customer demands. Various features like channels, infrastructure enhancements, cloud and big data adoptions, business analytics are getting implemented. This leads to complexity of the target application and also leads to difficulty in meeting the desired SLA. A tester can proactively identify issues by performing exploratory testing. This will act as proactive approach to simulate the performance testing during coding stage itself. In this paper, we use such an exploratory testing approach to test the enterprise modernized web application. We find out that the proposed approach is effective in bringing out major potential bottlenecks and predict how the SLA will get impacted during the simulation process.