Should I notch 4x4 post for 2x8 porch beams?
I understand you drawing. It is not using single point projection, as many of us learnd in drafting.  It is OK! IMHO (in my humble opinion) I would not use a 4x4 to sit a front &amp; side rail 2x8 on top of, with no notch (not great) or a notch (worse). If this is for a porch, correct?  You are going from a burried concrete pier, or a precast concrete pier, going up 1-3 feet?  I would use no less than a 6x6 or 8x8 with no notch.  Go to the top of the 2x8's and use at least 3 - 5/8" diameter bolts. No counter sinking either, but use carriage bolts. They have the button top, with a square shank, then the bol. Get bolts 1" longer than you need, only drill to the bolt size.  That will require a spade bit with an extension. Using a 3/8 to 1/2" chuck drill. Notching a 4x4 only gives you 2x4 + 2x2 to hang your joists on. With a 2x2 vertical support.  I'm a MORE is never wrong, kind of builder.  I've been at for 50 years.