Durablity

Source: Dev.to

Durability

Durability means that once a transaction is successfully committed, its changes are permanently saved in the database. Even if the system crashes, experiences a power failure, or encounters other failures, the transaction remains reliable.

In databases like PostgreSQL, this reliability is achieved through Write‑Ahead Logging (WAL). Before making actual changes, the system first records the transaction in a log file. If a crash occurs before the changes are applied, the logged queries can be replayed to ensure consistency.

Durability in Wallet Systems

Once money is transferred and confirmed, it will always be reflected, eliminating the risk of losing completed transactions and records for the user.

BEGIN;

UPDATE accounts 
SET balance = balance - 100 
WHERE name = 'Alice';

COMMIT;