At what stage are security checks done on the applicant?

While the case is being processed at the NVC - or - after the interview at the Consulate/Embassy?

I think I will be ssooooooooooo depressed if after the interview, the make us wait for security checks (which could have been done while the case was still at the NVC). Making us wait again.

Unfortunately the answer is likely to be both. I wish you the best!

from my understanding there's a lot of checks that can be requested. Some are certainly done before the case leaves DOS the first time but I was told by DOS they can occur at any time before and/or after the interview. In the country of orgin or at DOS. At least this is what someone told me at DOS when I called about our case.

From the letter my senator got from the embassy, the checks are started as soon as the DS 230 and other forms are received. When u go for the interview they will take the fingerprints, photos, etc, and send them for checks also. It is my understanding this takes only a few days. It is the name checks/job checks/prior travel checks that take forever.