How long mail takes is going to depend on many factors along the way. Many factors, indeed, though with regard to how long does priority mail take, the answer is, not long. In fact, the United States Postal Service says your package or envelope will arrive within two days.
Both the 2009 IRC and the DCA6-09 allow #2 southern pine 2x10s to span 13 feet 1 inch at 24 inches on-center at a design load of 50 psf. That means these joists can span the 12-foot depth of the deck, and the beam can be located at the perimeter. Nine joists will be needed for the 16-foot width.
You put the posts in, run the beams between them (a 2x10 on either side bolted in) , then cantilever the deck joists over the beams. deck.PNG 15.32KB 1 downloads. I build for a living and this is exactly how I would do it. The only thing I might change is since you are using 2x10 joists 24 centers would be just fine.