WSO2 DSS and JSON columns

Question

I have a Cassandra table with 2 columns: "id" and "Data". Data column contain a JSON data (near 30kb size).

When I use DSS SOAP to retrive this data it works fine just for one record. If I try to select 2-5 records it works very slowly and if I select more than 5 records DSS is hung up.

The same effect in case when I use MySQL.

Any ideas?