spring-data-jpa

Spring Data JPA pagination is implemented by returning `Page<T>` from repository methods that accept a `Pageable` parameter. Pass `PageRequest.of(pageNumber, pageSize, Sort.by(field))` to retrieve sorted, paginated results with metadata like total count and available pages.

Derived queries use method naming conventions (e.g., `findByEmail`) for simple lookups; @Query lets you write JPQL or SQL for complex filtering, joins, and aggregations. Use derived queries for straightforward cases and @Query when the logic exceeds naming conventions.

Spring Data JPA auditing automatically manages creation and modification timestamps and user information. Enable it with `@EnableJpaAuditing`, annotate entity fields with `@CreatedDate`, `@LastModifiedDate`, and provide an `AuditorAware` bean to capture the current user.

Yes, UUID primary keys work with Spring Data JPA. Annotate the field with `@Id` and `@GeneratedValue(strategy = GenerationType.UUID)`, or generate and assign UUIDs in code before persistence. This avoids sequential ID exposure and scales across distributed databases.

Configure multiple `DataSource` beans, create separate `EntityManagerFactory` and `TransactionManager` for each database, and partition repositories by package. Use `@EnableJpaRepositories` with `basePackages` to route each repository package to its corresponding persistence unit.

Add `@Index` annotations on frequently queried entity fields, create composite indexes for multi-column WHERE and JOIN predicates, and index foreign keys. Combine with derived query method names and @Query optimization to reduce full table scans and accelerate pagination.