Billing in asterisk

Hi ,

I Want to know how can i do billing in asterisk.
Following is the database structure.

Database :-Voip
Table :- Customers,CDR, etc.

Table Customers. (For the details of the customers)
CDR (Table for asterisk CDR)

I would like to know when a call is answered billsec is available in CDR table but for deducting the balance from the Customer table i have to create separate mysql connection(since i m using mysql as database.) means if there are 500 concurrent calls there will be 500 mysql connection running concurrently for updating the balance of the customer.
Is there any way asterisk provide to do the billing

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