I found Notion's URL schema interesting as well. They have to contend with renames of pages, reorganisation of the hierarchy and all that. So they have something like:

    notion.so/:account/Current-Name-of-Page-:pageid 

where the name changes if the page is renamed, but the redirect works, as the page ID is unchanged. In fact, one can just use

    notion.so/:account/:pageid 

and gets redirected to the right page, or even

    notion.so/:account/Anything-else-:pageid

works too...

This is very handy in my use cases, when various Notion data is extracted into another tool, reassembled, and then needed to have a link to the original page. I don't need to worry about the page's name, or how that name gets converted into the URL, or any race conditions....

The page hierarchy is then just within the navigaton, not in the URL, so moved pages continue to work too (even if this looks like a flatter hierarchy than it really is).

I'm sure there are plenty of drawbacks, but I've found it an interesting, pragmatic solution.