a third way...?

I can save session variables in server memory or I can leave them stored in the database and get them there. Is there a third place to store them while the user is online, like browser memory?

I'm asking because I want to know how many concurrent sessions can be handled by my web host and thus how many servers we should consider. They want to know if sticky sessions are required, evidently if they are required that would increase server demand and reduce the number of possible concurrent sessions.

Correct me please if I'm (probably) wrong but there is evidently a trade off between using the database and server memory to store session variables. If I use the database to store them, then that increases server usage in spitting stuff out, but would increase the number of concurrent users since the session wouldn't have to be sticky.

So, as I'm debating all this, I ran across 'browser memory'. Is that real, can it be used to store session variables and thus decrease demand on the server and increase the number of users that could be served from a single server, or am I dreaming?

Thanks!

Brian