The K-3 visa is now rarely used:
K-3/K-4 Nonimmigrant Visas
If you are a U.S. citizen and you filed a Form I-130, Petition for Alien Relative for your foreign spouse who is abroad, you can also file a Form I-129F, Petition for Alien FiancÚ(e). This is the first step for your spouse and his or her children to obtain a visa to come to the United States while you wait for USCIS to make a decision on the Form I-130. Historically, you and your family members might have been separated for some time while waiting for a decision on your Form I-130. Congress sought to resolve this problem by creating K-3 and K-4 nonimmigrant visas to shorten the time your family would need to spend apart. However, because USCIS now takes less time to adjudicate the Form I-130, the current need for K-3 and K-4 visas is rare.
I am not a regulated immigration advisor and am only providing my own personal views and opinions. This should not be relied upon as advice.