laravel 5.4: pessimistic locking. Avoid a row to be selected until transaction is finished

I am storing financial transactions in a database. For efficiency reasons in the transaction row i save the ammount and also the balance of the account. For example:

ID | TRANSACTION_AMOUNT | ACCOUNT_BALANCE

ACCOUNT_BALANCE in a new row is calculated as the last ACCOUNT_BALANCE + the new TRANSACTION_AMOUNT.

To proceed with this operation i need to do first a SELECT and then an INSERT. The issue is if two transactions came almost at the same time. Both of them will read the same last ACCOUNT_BALANCE and after the inserts the ACCOUNT_BALANCE with be inconsistent.

I have seen the function lockForUpdate() but im not completly sure how to use it for this case or even if apply.

Whats the best approach to solve this?

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