[vitalyd]

I think once you implement threaded i/o, requests for hot keys will hit in the cpu cache and you'll become NIC limited. At that point, read replicas is the best solution rather than shared memory since contention will move to NIC and adding more cpus won't help.

Edit: Salvatore, you should also look at the Seastar/ScyllaDB design (if you haven't yet) - that architecture would work well for redis as well. And if user has access to DPDK (or other kernel bypass enabled NICs, like Solarflare), their performance will go up even further.

[natebrennand]

The group behind Arrakis did some testing by bypassing the kernel through NIC's and the results were pretty amazing. They also made modifications to memcached and got similarly great results FWIW.

https://www.usenix.org/system/files/conference/osdi14/osdi14...

[acconsta]

Already exists for memcached!

https://github.com/scylladb/seastar/wiki/Memcached-Benchmark