How detailed do you want to get?

If you're using Python or C or something else to use redis as a server, it's probably just as fast as Q/KDB, and some informal benchmarking supports this:

    redis-server &
    redis-benchmark -t set -n 1000000 -c 1 -P 1000000
    0.00% <= 1368 milliseconds

v.

    q)h:neg hopen`:localhost:1234
    q)\t 1000000 h/"a:69"
    1013

However I don't think this necessarily a good way to build your system, because if you're going to do a million of (read something write) every second, and then do a million of (read store), then you might as well write it in KDB and just make it (read something store) and save yourself 40% on your heating bill.