CA 34 - Atomicity - Design a Reliable Wallet Transfer System with ACID Guarantees

Today I worked on a wallet system like GPay or PhonePe, where users can send money to each other. The main focus was Atomicity from ACID properties. Atomicity means “all or nothing”. If a transaction fails in between, everything should go back to the original state. Transaction I wrote a transaction like this BEGIN; UPDATE accounts SET balance = balance - 200 WHERE name = 'Alice'; UPDATE accounts SET balance = balance + 200 WHERE name = 'Bob'; COMMIT; Now Testing Failure I intentionally broke the second query (credit to Bob). BEGIN; UPDATE accounts SET balance = balance - 200 WHERE name = 'Alice'; UPDATE accounts SET balancee = balance + 200 WHERE name = 'Bob'; COMMIT; BEGIN - start transaction Do all operations If success - COMMIT If error - ROLLBACK Atomicity ensures no partial transactions, which is very important in payment systems.