Face API- find similiar faces

I need to implement face recognition using azure face api . I have developed a programme which is able to find similiar faces using .net SDK . For my use case ,I need to click photo of a person from the webcam and find matching faces from images kept in azure cloud storage . Now, there could be thousand of images in azure cloud storage and in my current implementation of face recognition ,I'm iterating through all the images(kept in azure cloud storage ) and then matching them with the webcam image . The concern here is : The face api (provided by azure ) charges 1 dollar per thousand call . Is there a way the search could be optimized such that i don't have to scan the faces which i have already scanned for previous searches