How would you structure the interaction between the server-side and the data storage?

For structuring interaction between backend and data storage, architectural patterns and layered structures are typically used.

The most common levels include:

• Data Access Layer (DAO, Repository) — responsible for direct interaction with the database or storage. Implements CRUD operations, queries, and data transformation.

• Service Layer — contains business logic, uses DAO for data retrieval and storage, processes data, and implements application rules.

• Controllers (API layer) — handle client requests, invoke services, and return responses.

This approach isolates data handling logic, simplifies testing and maintenance.

For database interaction, ORM (like Hibernate for Java) or direct SQL queries via drivers are used. Error handling, transactions, and caching are also important for performance.

Example in Java with Repository pattern:

public interface UserRepository {
    User findById(Long id);
    void save(User user);
}

public class UserRepositoryImpl implements UserRepository {
    // Database access implementation
}

public class UserService {
    private UserRepository userRepository;

    public User getUser(Long id) {
        return userRepository.findById(id);
    }
}