How can simultaneous modification of the same data by multiple users in a database be prevented?

To prevent simultaneous modification of the same data by multiple users in a database, mechanisms of locking and concurrency control are used. The main approaches are:

1. Optimistic Locking — assumes conflicts are rare. When updating data, it checks that the data has not changed since the last read (for example, using a version or timestamp). If the data has changed, the operation is rolled back.

2. Pessimistic Locking — locks the data during reading or before updating so that other transactions cannot modify it until the current transaction is completed.

In Hibernate, optimistic locking can be implemented using the @Version annotation:

@Entity
public class Product {
    @Id
    private Long id;

    @Version
    private int version;

    private String name;
    // other fields
}

When updating, Hibernate checks the version and throws an exception if the data has been modified by another user.

Thus, the choice of approach depends on performance requirements and conflict frequency.