Ok. I admit using Kafka as DB is not straight forward but just stating it doesn't provide ACID functionality is not enough.

The example they give is very simplistic. With the correct design of kafka topics and events the problem of the example can be fixed.

And according to oracle https://www.oracle.com/database/what-is-database/ :

> A database is an organized collection of structured information, or data, typically stored electronically in a computer system.

So Kafka clearly fits that definition.