GET and SET (and similar) are easy, let me know if you keep the same performances once you start to need RMW operations or even transactions to deal with multi keys commands or add clustering support :)

Also going faster than Redis doing only GET and SET is fairly easy, the very very very early versions of cachegrand (pre 0.1) were doing well over 100M/s of GET and SET on a 32 core / 64 threads machine with pipelining.

Once you start to chuck the rest to make it actually "usable" it's where you start to massively lose performances.