This blog has no database
Where do your posts go when you hit publish? Into a signed cookie in your browser, and nowhere else.
A demo should be easy to deploy and impossible to spam. So instead of a database, this blog stores new posts in a signed cookie. The server can trust its content, since it was signed with a secret, and every visitor only ever sees their own posts.
Cookies are small, so the oldest posts are dropped once the cookie is full. Clear your cookies and the blog is back to these example posts. A real blog would of course load its posts from a database or a headless CMS, but the routes would look exactly the same.