No scaling guru here, but did this quick calculation for fun (gotta love C-x-e): (/ (* 150000 ; users 3.5 ; times per min (+ 5 ; cookie length

No scaling guru here, but did this quick calculation for fun (gotta love C-x-e): (/ (* 150000 ; users 3.5 ; times per min (+ 5 ; cookie length 7.5 ; chars per post ) ) (expt 10 6) ; bytes per MB ) Evals to ~6.6. Double that (for max capacity estimate) = 13.2. Unit is MB/min, which is ~0.22 KB/sec. One hour is just short of 800 MB of plain text data. A gig of DB seems reasonable (I don't know what extra overhead is associated with, say, a CHAR(15) field). Like Rectic said, a RAM based database seems better. PS sorry, I don't know how to format code here.