As far i know, In bitcoin there is no where storing the account balance in db straight forward. If the person wants to know his account balance from his client app the server will calculate all his transaction of credit and debit return the sum value.
If this above is true when person A has previous transactions like 20,000 and Person A wants to transfer some money he has to Person B.
When this process starts the bitcoin mining server has to calculate all his transaction from beginning to check whether the person A has enough balance or not and this has to be done in other mining server also to verify.
In this case as long as the person has 1 lac transaction, to calculate the balance the computation process will be heavy right ? more computation process uses more cpu cycles and power which affect the maintain cost of the computer and transaction fee may go high.
Please explain how its happening ?