Yes. as the article points out there's no way to reject an event based on some criteria that keeps the events internally consistent. for instance, two people can't check out the same item of inventory = 1. you need to first validate this event on the materialized view of the commit log to make sure the item is still available. however, what happens when your validation goes out of date? For example, what if there's an event checking the last inventory in the event log but the materialized view doesn't reflect that yet? you end up checking out the same inventory twice and promising it to both customers! not good.
DBs can solve this through optimistic locking (atomically making sure my new event applies to the version number of the previous event + 1, otherwise failing) but there's no way to do this in Kafka as far as I know (however, as this is a problem i'm currently facing, please feel free to let me know if there is)
