https://www.kvisas.com/K3-Visa.shtml
"
National Visa Center (NVC)
When the USCIS has approved the CR1/IR1 visa petition, it is forwarded to the National Visa Center ("NVC") where original documents are reviewed and background checks are performed on both the petitioner and the beneficiary. The NVC will forward the petition to the Consulate that will conduct the visa interview. The Consulate will not interview the foreign spouse until the NVC checks have been successfully completed."
