# Architecture of the Event system

The event system handles data generated by the creation and usage of passes.
It works asynchronously by producing the data as an event and providing it in a message queue.
It then can be read by one or more consumers to be further processed, like being stored in a third-party system.

```{todo}
add a mermaid diagram to illustrate the flow
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The event system in its core

1. takes information from callback services or other producers,
1. stores the information temporarily in a message queue
1. information gets consumed and is further processed

Examples of types of information handled:
- applications for passes and updates to those applications (common identity pass/ service pass)
- pass creation/ update from vendors via callbacks
- handle data generated by MaSA, like a check-in to an event.