My understanding is that event_id is not unique.
I am using JSON to send / retrieve events from a network server.
I would like to pass by my proposed solution to see if you can see any issues.
On creating events I will send to the network server the event_id DHTMLX allocated.
In the successfull response to the POST for this information I will send a new_id allocated by the database and call changeEventId.
All subsequent GET / POST for retrieving / updating events will work on the DB allocated event_id.
I was not intending to save the original event_id allocated by DHTLMX in the database unless you can point out a reason for doing this.