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You can use more connections than 65k, since connections are identified by srchost, srcport, desthost, and destport. You are restricted to 65k NATted connections to a single server's* web site, though.

*Assuming the server is using a single IP.

Good point, but still, there aren’t that many google, instagram or windows update IPs. I can easily imagine more than 1% of the 10 millions people connecting to google simultaneously.

I'm not an expert in this field, but I did come across the carrier-grade NAT range on a very odd project:

https://en.wikipedia.org/wiki/Carrier-grade_NAT

I can't recall, does TCP require that src:srcport->dest:destport pairs be unique, or is there another way to distinguish connections (sequence numberd maybe?)? I guess there are other IP protocols like UDP though...