SEO specialists always check if the website can give a 404 response. They enter a site domain slash a random set of letters, for example, https://www.amazon.com/kjdfhgnvnoe
and send it to a service checking the server response.
If the site returns a 404 response, everything is okay. If it returns any other response, for example, 200 or 302, it is a big problem, because an unlimited number of site pages with random URLs will be included in the website index, negatively affecting SEO ranking.