  In hadron collider experiments, triggering the detector to store interesting
events for offline analysis is a challenge due to the high rates and
multiplicities of particles produced. Maintaining high trigger efficiency for
the physics we are most interested in while at the same time suppressing high
rate physics from inclusive QCD processes is a difficult but important problem.
It is essential that the trigger system be flexible and robust, with sufficient
redundancy and operating margin. Providing high quality track reconstruction
over the full ATLAS detector by the start of processing at LVL2 is an important
element to achieve these needs. As the instantaneous luminosity increases, the
computational load on the LVL2 system will significantly increase due to the
need for more sophisticated algorithms to suppress backgrounds.
  The Fast Tracker (FTK) is a proposed upgrade to the ATLAS trigger system. It
is designed to enable early rejection of background events and thus leave more
LVL2 execution time by moving track reconstruction into a hardware system that
takes massively parallel processing to the extreme. The FTK system completes
global track reconstruction with near offline resolution shortly after the
start of LVL2 processing by rapidly finding and fitting tracks in the inner
detector for events passing LVL1 using pattern recognition from a large,
pre-computed bank of possible hit patterns. We describe the FTK system design
and expected performance in the areas of b-tagging, {\tau}-tagging, and lepton
isolation which play and important role in the ATLAS physics program.
