Firebase Feature reqeust: asynchronous trigger and access control

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A simple use case about firebase trigger:

I have a stocks table(tb_stocks):
GoodsID,GoodsNum,Quantity
1,KK0245MM08-804-M,98
2,KK0172YY02-990-L,18
3,KK2104MM681-990-XXL,20

And an orders table(tb_orders):
OrderID,UserName,GoodsID,Quantity,CreateTime
1,Andy,3,1,2012-11-29 11:01:01
2,Bob,2,1,2012-11-29 11:02:01

I very much desire a trigger feature in Firebase:
When a user make an order from his/her mobile phone, for example, a new line inserted into orders table:
3,Jack,2,1
then the trigger function will decrease KK0172YY02-990-L's stock quantity from 18 to 17.

If my shopping app is very popular, i will need a asynchronous trigger that at every 5 minutes summarize all orders in 5 minutes:
1,Jack,3,1,2012-11-29 11:01:00
2,Evan,3,2,2012-11-29 11:04:00
The updates of stocks table will be triggered only once at 11:05:00, the KK2104MM681-990-XXL's quantity will be updated from 20 to 17.

The user will be verified by Firebase,
and a user can insert data into the orders table through my mobile app(with ajax actions), //TABLE LEVEL INSERT privilege allowed
a user is not allowed to access stocks table,                                              //TABLE LEVEL ALL privilege denied
a user can modify the hashed password in the row of users table(tb_users):                 //ROW LEVEL UPDATE, TABLE LEVEL INSERT privileges allowed
UserID,Username,Hash
1,Jack,2c7a6c784d9d8cdd9cf5c4f3bb9a0dfd
2,Peter,05e66fbd3725a7cf2de8535a64b24da7