I know this topic is more then 3 years old but I like to tell my 2 cents, for the same problem I developed an Event Sourced Akka Finite State Machine with Cassandra to deal Command/Write Side of the CQRS.
As the previous, I have the agree that write side model and read side model, does not have to be the same, in my State Machine there are more then 30 States but only 5 of those are only interesting for Read Side.
If anybody like to see how it is done, I wrote a Blog about it [Akka Finite State Machine with Cassandra/Elasticseach for CQRS][1]

[1]: https://mehmetsalgar.wordpress.com/2022/04/18/a-model-driven-event-sourced-cloud-ready-application-with-akka-finite-state-machine-using-kafka-cassandra-and-elasticsearch/

I know this topic is more then 3 years old but I am also using Elasticsearch for the read side of the CQRS but I think there are other platforms fitting better to write side but it is not just a database technology, in todays Event Sourced paradigm more is necessary, I am using Akka's Finite State Machine with Cassandra, which in my opinion fits better that sort extreme write loads better then Elasticsearch.
I wrote a blog about it, if anybody likes to see, [Write Side for Elasticsearch CQRS][1]

[1]: https://mehmetsalgar.wordpress.com/2022/04/18/a-model-driven-event-sourced-cloud-ready-application-with-akka-finite-state-machine-using-kafka-cassandra-and-elasticsearch/