what's better way to store a million keys in mem?

Hi,

A application, needs to check whether a user already logined, by
looking at static var in memory.

I don't have good idea. what's doing is, use Hashmap <not sure
Hashtable is better interms of inserting/removing/finding> to store ID
<string> -- key and status <character> -- value.

question:
what the better way to implement this goal, it should support up to 1
million of keys, in terms of high inserting/removing/finding, and
happened more frequently.

--
Thanks
John
Toronto

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