To answer your question, api link rather than full data let's take a sample:
In Amazon, Order Microservice sends a event OrderCancelled and Customer service listen to that event.
Now there could be two ways of sending the event data:
- Send complete order data in the Event
Pros: Listener services do not need to query Order Service for their functioning.
Cons: Lots of data will be passed in the event even though only 10 % is used. Lots of I/O.
- Send only order id, cancel reason , customer id , date in the event
Pros: If the data is choosen carefully, much less data is sent in the event.
Cons: If the data is choosen incorrectly, then that means lots of API requests.