DDoS Attack on Bitotsav '19 Website

This is not a technical write up. This is a story that I want to share which might be a lesson for several Web & App developers out there. Bitotsav is the annual cultural fest of BIT Mesra and the Tech Team was responsible for developing the Website and the Android App. There were 46 events in the fest and we were responsible for sending out updates (announcements, results, etc.) for each event to the app. 16th February 2019, on the 2nd day of the fest, the website started experiencing problems. The website got slower and slower. The website was hosted on Microsoft Azure Virtual Machine. It was evening around at 5:00 PM. I checked the logs for the Virtual Machine. In the past 6 hours, 700 GB of data was uploaded and downloaded from the server. The Virtual Machine had 4 VCPUs and all of them were being rigorously used. Due to such huge traffic, all the APIs stopped responding. The app was no longer usable. No updates could be sent to the participants. What was happening? In the