Ewallet — Code

... or create category, option selection, items by your self - Support create discount (etc kitajagakita 10%, openingdiscount 15%)

function transfer_money(sender_id, receiver_id, amount, idempotency_key): # Check if this exact request was already processed existing_txn = database.query( "SELECT * FROM transactions WHERE idempotency_key = ?", idempotency_key ) ewallet code

He checked his bank account. The $4,200 deposits from Axiom Logistics? They weren't there. They had never been there. His real job, the one he went to every day in the glass tower on 5th Street, had been paying him $17.50 an hour. The pay stubs were in his email. He’d just… stopped reading them two months ago. They weren't there

# 2. Lock Sender Wallet sender = db.execute( "SELECT current_balance FROM wallets WHERE id = %s FOR UPDATE", (sender_wallet_id,) ).fetchone() The pay stubs were in his email

Imagine User A has $100. They try to buy two items costing $80 each at the exact same millisecond. Without proper locking, the code might check the balance for both requests, see $100, and approve both, resulting in a negative balance.

But that wasn’t true.

Then his phone buzzed one more time. Not a text. A push notification from an app he'd never downloaded, with an icon he'd never seen.