image processing - Can SIFT run in realtime?

You can use ORB which is really fast.
Or tune up the SIFT/SURF/algorithm options.

OpenCV 3.1.0 now has several algorithms, such as KAZE & AKAZE - the latter is perhaps the very best image detector&descriptor as it shows great results with its (fast explicit) diffusion scale space. The previous SIFT&SURF are moved to the 'extra' repository.

Nevertheless perhaps what you want is to improve the matcher algorithm. In that case try to use FLANN (also in 3.1.0).