This is the default programming model in Go, but it's the same for Node.js, and you can use an easy-to-use event library in Ruby and Python as well.

A key-value store is system programming. It should be carefully designed, it's not real-world that you accept the default I/O model of the language you are going to use.

p.s. in the case of C it's hard to argue what is the default I/O model. It supports threads, fork, multiplexing, blocking and non blocking I/O, in the same way basically (in a low level way).