Minimise queries in Dynamo db

The current data model I designed has Organisation table and GroupData table.

Org Table has org_id as primary key. It also has a Global Secondary Index(GSI) with type_field as primary key so that all the Organization with a specific type_field can be retrieved.(type_field is mutable in Organization )

GroupData Table has org_id as primary key and month_year as sort key . For a given org, all the months data can be obtained by querying with a filter is_valid=true

Org Data  
{
  "org_id":"123sdfhsdkfhskdfhkdshf",
  "type_field":"25:50:25:0",
  // other atrributes
}

GroupData 
{
  "org_id":"123sdfhsdkfhskdfhkdshf",
  "month_year":"2017-02",
  "is_valid":false,
  "groupData":{//20 attributes},
  //other atrributes
}

I have to query GroupData for all the organizations with a certain type_field for 6 months .

The solution I came up with is 
 1. Query all the organizations for that type_field. 
 2. With the obtained Org ids , do the batch GET from Group Data . So, if there are 1000 organizations I have to do 6*1000 queries in Batch get. 

Is there any better way of modifying the data model so that queries can be faster ?