There are probably fewer than 100 websites that couldn’t be a single Postgres instance on nice server hardware, with good caching.
What makes you say that? AFAIK, the largest single dedicated servers you can buy on the market go up to around hundreds of cores and terabytes of ram, and NVME up to a PB~ish if you stack NVME/SSD/HDD as well. this is when i last checked.
Not everything on the internet is a “website” and then there are several website hosting platforms that aggregate the individual concerns.
Yeah, this is our read with Postgres here at Motion. I believe that Motion will easily be able to 10x on modern hardware along with various optimizations along the way.