Small fix duplicate check in spring boot

I am looking for a skilled Spring Boot developer to fix a small issue regarding duplicate checks in my project. Currently, when a duplicate is found, the system ignores it. However, I would like the desired behavior to be that it throws an error instead.

Ideal Skills and Experience:
- Strong proficiency in Spring Boot
- Experience with handling duplicate data
- Knowledge of error handling and exception handling in Spring Boot

Please note that there is no specific deadline for this task.