Why are you 3betting A3 off in the big blind?  It flops horribly and it's not too unrealistic he'll just flat you with A8 or A9.  Maybe there's some meta going on here i am not familiar with but I'm not a fan of the small 3bet with such a poor post flop hand :)I like the river call, i mean it's very difficult to put him on a hand that flats a 3bet here and connects with that flop, maybe K9, Q9 J9 T9 or something, those are the only hands I can see and they seem pretty unlikely, his line doesn't make sense with any other hand and you'd feel like with a 9 he'd still bet the turn, plus if we account for the flush he'd need to bet the turn also to get any value from his hand.

One of the useful things about 3betting such a hand is that you have an A blocker at least. I suppose if you don't monkey away your chips every time an ace flops it should be fine. I never have the balls to call in these spots, but it looks like some good poker to me :) Tis true that there's not much he can have here as a value bet that wouldn't have bet the flop or turn.

How can you not monkey away your chips when an A flops?  Surely thats the whole point of this 3bet?  If an A flops and we bet, then he shoves I don't see that we have much choice but calling given how we played the hand - if we're not willing to get it in with top pair then we really shouldnt be 3betting this at all.

I hate the 3bet with A3o, you're essentialy playing 1 card here & are dominated by nearly every other Ax. Unless you've played this guy a ton I can't see meta is a justification as the number of 3bets can't be that high for him to put you on an accurate range. As played, I agree with soulouri, he's repping nothing on the river. I can't see him checking 2 streets with 9x or 7x, only other possibility is a small PP.