Here is how a robust transfer function looks in a backend language (like Java or Python):
# 3. Lock the receiver's wallet row receiver = SELECT * FROM wallets WHERE id = receiver_wallet_id FOR UPDATE; e wallet code
# 5. Update the cached balances in the wallet table UPDATE wallets SET current_balance = current_balance - amount WHERE id = sender_wallet_id; Here is how a robust transfer function looks
Network failures happen. A user might click "Pay" twice, or the API might time out while waiting for a response. Without safeguards, this leads to double-charging. A user might click "Pay" twice, or the
Every digital wallet, whether it’s PayPal, GCash, or a custom fintech app, relies on these key modules:
Imagine two API calls trying to deduct from the same balance at the same time. Without proper locking or database transactions, users could overspend.
| Feature | Tech Suggestion | |---------|----------------| | User auth | JWT + refresh tokens, 2FA (TOTP) | | Balance storage | PostgreSQL with row-level locking | | High-frequency txn | Redis + async job queue (Bull/SQS) | | QR code payment | Generate static/dynamic codes with expiry | | Transaction history | Materialized view or separate read replica |