<span class="q"> It sounds like it'd be cheaper and allow you to make better use of cache, so I'd assume it's good.<br>
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<div><span style="WHITE-SPACE: pre"></span>Being able to rely on a cache will impact your design and will generally be good. I do some things very similar to this that involve grabbing some list-like data, and then fetching items related to items within the list. As many as I can get come from cache, and the rest have to be fetched from the source, and then placed back into the cache.
<div>How about storing the list of the user's friends in cache also? The only problem here though, is what if the user has tens of thousands of friends, for instance?</div>