How to perform Redis client side caching of a Sorted Set, by rank

Question

I have an application which pulls the 'top ten' from a Redis Sorted Set. That is, the members of the set with the highest ranking, eg ZRANGE top40 0 9 REV . I would like to cache this result on the client and be informed by the Server when the members of this subset change.

From my research so far, I have understood that Redis server-assisted client-side caching (RSACSC) is implemented such that the server keeps a record of the keys which are requested by each client and will inform that client (or another) when the keys change . This would imply that the server is not tracking their rank within a Sorted Set.

What I want to achieve is this:

1. I have a Sorted Set which contains the Top 40 songs, ranked by number of streams
2. I have a (Python) client which fetches and caches the highest ranking 10 from the Top 40
3. If a new song comes in at number 5, the server will send an expiration message for either
   • cached members 5-10, or
   • the entire cached subset of 10 members

I would like to understand if RSACSC can accommodate this as-is. If not, can it be achieved using other Redis trickery, for example somehow storing the Top 10 server-side as a new key and pulling this key into the Python app.

I would hugely appreciate an example using a Python client, although the main purpose of the question is to better understand RSACSC and its limitation regarding Sorted Sets, plus any workarounds.

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Having done some more research, and using a real-world dataset (and following the positive confirmation from @guyroyse), it seems that any change to the Sorted Set results in a client invalidate notification, even if the change happened outside of the subset of members that the client requested. Redis does indeed appear to treat the entire Set's key as a single entity, rather than track the client's request for and range of members.

In this way, (3) is not possible. Therefore this becomes a question of workarounds, eg some server-side ability to automatically store the subset as a separate key.

Answer 1

Having done some more research, and using a real-world dataset, I can confirm that any change to the Sorted Set results in a client invalidate notification, even if the change happened outside of the subset of members that the client requested. Redis does indeed appear to treat the entire Set's key as a single entity, rather than track the client's request for and range of members.

In this way, (3) is not possible.