We are running load test for POST calls and we observed that for 100 concurrent users time goes up to 16 seconds per request. After some findings we come to know that no load on database but many requests at Drupal server are in wait state and sends request after 5-10 seconds hence we get delayed response back on website.
We are not able to identify that this wait is for what? (database connection/ Drupal level processing is going on / something else)
Any pointers/ suggestions are helpful in finding out the solution for this.