If it were mine, I wouldn't try to attach the spliced beam ends to the 4 x 4 posts with 4 bolts. What you're proposing doesn't leave enough "meat" between the edges of holes and ends of members, and actually creates weak points at both the beam ends and the back-side 4 x 4 posts. Wouldn't be an issue if you had used 6 x 6 posts, as the IRC requires. A much stronger connection for your situation would be to use 6 through-bolts, 2 longest drilled into the gap between beam ends (with mender plates), and also going through a centered rim scab on the outside; the other 4 shorter ones could then be located farther away from the beam ends, going through them and the outside scab, but not connected to the vertical post. Posts and beam ends would be much stronger doing it that way, and wouldn't be likely to fail when you load the deck with 15 tons of people.