If you want to just visualize data in Casandra you can look at this project
https://zeppelin.apache.org/
If you want historical and other data of your database
Logstash JDBC Connector would work.
I agree with DaDoonNet, that it is good to have the application send the data to PostGres and ELK for more real-time data but that is an architectural and requirements needs
https://www.confluent.io/blog/bottled-water-real-time-integration-of-postgresql-and-kafka/
once in kafka you can use logstash to consume and insert to Elastic