Preventing Duplicate Contact Creation of incremental run of CRM Data

Hi,

I am working on removing duplicates from CRM. I have worked on deactivating duplicate records having same email address. And created a table in Database storing inactive customer's id mapped to GoldenCustomer's id. Now, i want to write a plugin in which i want if next time duplicate record comes in incremental, it will fetch data from this stored table and won't create a new record. 

Any suggestions on how to proceed with this approach?