How Spring Data JPA, JPA, and Hibernate work together

The Magic Line That Raises the Right Question

Spring Data JPA is a library that lets you query a relational database by writing a Java interface method and nothing else: no SQL, no ResultSet parsing, no PreparedStatement boilerplate. You declare what you want, and the framework figures out how to fetch it.

Here is the moment that stops most backend engineers in their tracks:

public interface UserRepository extends JpaRepository<User, Long> {

Optional<User> findByEmail(String email);