I built a deck for my pool 7 years ago. I don't pretend to know everything, nor am I saying my way is the best way, but so far it's held up well. Couple things I found out:
First off especially if you're an old fart like me, get some young bucks to do the manual labor of digging post holes. As you can see I made sure they had a supervisor on site.
I built a 16'x16' square along the side of my oval pool using 4x4 posts, double 2x10 beams and 2x6 joists on 16" centers. After 7 years it's very solid and I can't see any sag.
I continued my deck around one end and down the other side. Making the deck match the contour of the round end takes some work but I think it adds a lot to the deck.
I was happy with how it all turned out even though when I posted about it before I had some members telling me it was a real hack job. Fortunately I don't care what they think.
I hope this will in some small way help you. For the record my posts are set in concrete which hasn't caused any problems so far, but then again it's only been 7 years.