In Calendar the event is added to the store automatically, then the editor is opened. But on editor cancel it will be removed from the store. So in case of autoSync true this will cause lots of unnecessary requests, but should not populate lots of records in the database. There is a ticket to fix it: https://github.com/bryntum/support/issues/2023
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You could use the beforeSync
event on your Calendar's CrudManager and if what you detect in the update packet (I am not sure of the structure of that, you would have to set a breakpoint in your code and examine it) if the temporary record, return false
.
https://www.bryntum.com/docs/calendar/#Scheduler/crud/AbstractCrudManager#event-beforeSync