In a Spring Boot application, you can map application-specific exceptions to HTTP status codes using the @ResponseStatus annotation in custom exception classes. This allows you to define the specific HTTP status code to return when a particular exception is thrown, providing fine-grained control over error responses. The other options are not standard practices for mapping exceptions to HTTP status codes in Spring Boot.

The correct annotation to secure methods in Spring Security is @Secured. This annotation allows you to specify which roles or authorities are required to access a particular method.

The @DataJpaTest annotation in Spring Boot is used for testing the persistence layer. It slices the application context and loads only the relevant beans related to data JPA, making it efficient for testing data access operations.

The most efficient way to manage transactions in a Spring Boot application utilizing Spring Data JPA is by using declarative transaction management with the @Transactional annotation. It simplifies transaction handling and provides better readability and maintainability. The other options may work but are not considered as efficient and convenient as declarative transaction management.

The most efficient way to manage transactions in a Spring Boot application utilizing Spring Data JPA is by using the @Transactional annotation on the service layer. This annotation simplifies transaction management and ensures that all methods within the annotated service class are executed within a single transaction. Embedding SQL transactions within repository methods can lead to issues with transaction boundaries. The other options are not best practices for managing transactions in a Spring Boot application.

The purpose of the @Primary annotation in Spring is to specify the primary bean when multiple beans of the same type exist. When multiple beans qualify as dependencies for injection, the one marked with @Primary is the one that Spring will choose by default. This is useful in scenarios where you have multiple implementations of an interface or class, and one should be considered the primary choice.

In Spring, method security expressions allow you to specify security constraints using SpEL (Spring Expression Language) within annotations like @PreAuthorize or @PostAuthorize. This enables fine-grained control over method-level security. Custom security annotations (Option 1) might be used in combination with method security expressions, but they are not a replacement. URL-based security (Option 3) and a single global security rule (Option 4) are not the preferred way to achieve fine-grained security.

To optimize the database interaction layer of a high-traffic Spring Boot application, implementing connection pooling with HikariCP is a recommended strategy for superior performance. HikariCP is a widely used connection pooling library known for its efficiency. Increasing the connection pool size is generally a good practice, but HikariCP provides better performance out of the box. Using a single shared connection is inefficient and disabling connection pooling is not advisable, as it can lead to resource contention.

To create a custom constraint annotation in Spring Boot, you need to create an annotation interface and a corresponding ConstraintValidator class to implement the validation logic. The ConstraintValidator interface allows you to define custom validation rules for your annotation, making it a crucial part of custom validation. The other options are not standard components used for creating custom constraint annotations.

In a large Spring Boot application with multiple modules, organizing and managing configuration properties efficiently can be achieved by structuring properties hierarchically, matching them to the module's package structure. This approach promotes encapsulation and ensures that each module has its own configuration properties. Placing all properties in a single file can lead to conflicts and make it challenging to track changes. Hard-coding properties lacks flexibility and maintainability. Using a version control system is important for tracking changes but doesn't address organization directly.