Appears that the AWS service has the '_delete_by_query' API installed in 5.3 . Strangely (and I have only tried this for teh last hour) , it works through their K4 interface, but not through teh curl commands from a different node... will track tat down. They don't have the delete-by-query plugin installed yet.
So at least I am relatively happier 
Just thought I would put an update here.