Atomicity - Design a Reliable Wallet Transfer System with ACID Guarantees

Atomicity – Reliable Wallet Transfer with ACID (Simple) When I learned about ACID properties, the one I understood first was Atomicity. It is very simple — it means all or nothing. I can explain this using a wallet transfer example. What I am trying to do Let’s say: Wallet A has ₹1000 Wallet B has ₹500 I want to send ₹200 So internally, two things should happen: ₹200 should be deducted from Wallet A ₹200 should be added to Wallet B The Problem If only one step happens, it becomes a big issue. Example: Money is deducted from A But not added to B Now ₹200 is lost. This is not acceptable in real applications. How I Solve This To avoid this, I use a database transaction. BEGIN; UPDATE wallet SET balance = balance - 200 WHERE id = 'A'; UPDATE wallet SET balance = balance + 200 WHERE id = 'B'; COMMIT; If everything works fine → COMMIT If any error happens in between → ROLLBACK; This cancels all changes and keeps the data safe. Why Atomicity is Important No money loss No partial updates Syste