Flying via SVO is not an issue. I also went to TBS via SVO this year and usually transit once or twice a year via Moscow. Follow transit signs to transit desk. Get onward boarding pass. Immigration will review your passport (you are NOT entering Russia!) and then you go through security. Done. Usually takes about 15min all together. Can be a bit longer if the middle of the night or such as some of the staff are sleeping in the back room or such.