When should transactions be used?

Transactions are necessary when it is important to ensure the integrity and consistency of data during the execution of multiple related operations with a database. It is especially important to use transactions if:

• You need to perform several queries that must be atomic — either all succeed or none are applied.
• There is a risk of failures or errors during execution, and you need to roll back changes in case of failure.
• It is necessary to avoid race conditions during concurrent access to data.

In Java, transactions are often used when working with databases via JDBC or ORM (e.g., Hibernate), as well as within the Spring Framework with the @Transactional annotation.

Example of usage in Spring:

@Service
public class UserService {

    @Transactional
    public void transferMoney(Long fromUserId, Long toUserId, BigDecimal amount) {
        // operations for debiting and crediting money
    }
}

Here, the transaction guarantees that both operations will succeed together or not at all.