Index on Global Temp table

 Hi We are usging XLA Bulk event creation API , on that we are populating one gloabl Temp table with raw data and call the API one API is completed it updates event_id back in GTT , Now we are querying it again so that to get the event id for record we had populated . 

So are facing performance issue on that . So i have created normal index on that GTT for column that is holding the key value so that i can tie back to my staging table . it has improved performance .

So just wanted to confim it is ok to create index on GTT .because what i know is that index value will be appilcable to that session only like data and one session end it will be lost . So it will not cause the size problem as well .