# Why doesn't Cronofy issue event ids?

We don’t issue IDs to events, instead we require that developers provide an `event_id`when upserting an event to a user’s calendar. This is then used to identify the event when making subsquent updates/deletes.

This ID must be unique within the scope of your application’s `client_id`.

The rationale for this is two-fold.

- When inserting an event, your application doesn’t have to block, waiting for a response from a third-party system in order to receive the ID.

- Your system doesn’t have store any mapping between your internal IDs and external IDs



---
[Read in HTML](/developers/faqs/event-management/event-ids/)