[reipahb]

The only way I see to solve this without server side state is to replace the page-parameter with a list of items you have seen. The more button would then just find the top 30 items you haven't previously seen. Unfortunately, this would become unwieldy very quickly, and sooner or later you hit the browser limitations on maximum URL size.

A relatively simple approach that involves server side state is to periodically (once a minute?) generate the list of (for example) the 10000 top items.

(A high traffic site will most likely want to do this in any case, so that it has a cached list of items ready to serve to clients, instead of issuing a database query to find the top items for every request.)

Now, instead of overwriting the list of top items every time you regenerate it, keep multiple versions of the list. Then you can make the link to the next page specify the version of the list and the page number. That way, users will browse through one specific version of the list.

(This requires storing some state on the server, but the amount is relatively small. You control both the size of the generated list, how often new lists are generated and how long they are kept, so there is an easily calculated upper bound on the amount of state information you need store.)

[karmakaze]

This solution satisfies my usage and doesn't use a continuation token, though one could be constructed from version and page. It does however expire.

I can see that the other comments on constructing continuation tokens won't work for HN assuming post upvotes are mutably updated.