Concurrent user visualization

[LeeDr (Lee Drengenberg)]

You might try this;

Display concurrency in data on Kibana

I have fields with start date and duration (seconds) representing start and duration of a phone call. I would like to define concurrency (a number) when the same destination (also a field) is active within the same duration. That is if a ncall starts now for 30 seconds and another call to the same destination starts 15 seconds into the first call, concurrency should be 2 for the remaining 15 seconds. How do I define this in Kibana visualization as a line graph over time?