Caching Information

[eluser]Unknown[/eluser]
Got a question on DB Caching (sorry if I should already know this...)

I have a DB with 500K+ rows and is really used for look up, a lot, but from many users across. So, it isn't really tied to a particularly long session (the time of the query really)

So, my question is -> Is the cache file created when a user creates a session, and is for the life of the session OR, is that cache available to ANYONE on that particular server?

Use case -> Mobile Device needs to check for an item in a list before it can proceed. It passes that item via the web page and the return is a yeah or nay. The list changes once a day or once a week even, so it would be a great candidate to live in a cache, but i don't want or need to cache it if it is tied to a one time request.