When your file arrives it is assigned a B File number and BF date assigned for Prescreening.
Next step "Prescreening" - where they go through your application and see if they need anything else from you, note the file with a brief synopsis of the development of your relationship, possibly any red flags they have about you etc. They also document everything you submitted as proof of relationship, supporting documents etc. If they need something more, you would be sent a letter requesting those documents to be sent in within 90 days of receiving the letter.
This is usally done by junior officers/assistants as there are only a few senior visa officers in the embassy that can make final decisions on the application.
It then gets assigned a new BF date either to decide the file (interview or no interview) or to confirm that whatever they asked you to send has arrived.
If there are a lot of applications ahead of you, your file has red flags that requires further investigation of the applicant, missing information from the file etc, the BF date could be delayed making the wait time longer .
Hope that helps.
Sangria
