Try creating index on ACCOUNT (ACCOUNT_TYPE_ID,ACCOUNT_ID) , & check if inner query FTS gets removed by Index Scan
Else and a.ACCOUNT_ID not IN condition need to change as not exists
As of now i have removed the union all statement as after removing also i was getting the same result and in just 0.36 ms. I have sent to the dev team and waiting to hear from them .
Many thanks for your help. I SHall try with creating an index once i get a reply from them