Camunda API to start a BPD process taking time

Hello guys, we are having 2 camunda engines deployed on open shift platform. First camunda engine performs some validation and calls the second camunda engine using the mentioned api http://localhost:8085/process-controller/rest/process-definition/key/BPD_ERS_EC_ACTIVATION/start. When we are performing load testing 50 to 80 TPS, we are seeing that the start activity of BPD_ERS_EC_ACTIVATION takes lot of time to initiate. This delay increases with load. Can u please suggest any specific tunning configurations or any other approaches to reduce this latency, pls note we are also sending json information in the body of the request.