I think Amazon is very much on another level in terms of scale. Not trying to be negative about Shopify — they have a very large system to maintain - but Amazon is just on another level.
Combined Shopify sales are ~half of Amazon's but growing quicker. Shopify probably supports more sales per engineer than Amazon's retail stack team.
Shopify is not far behind Amazon (the e-com business). It's network sees as many unique visitors as Amazon, though I imagine Amazon has more sessions per visitor, but the GMV across Shopify is just shy of half of Amazon. It's still in the same ball park.
Amazon don't seem release any figures but I've seen estimates of 50,000 to 100,000 engineers. They do have 1.576 million employees worldwide (2025 figure).