Trying to grasp some basics of Redis I came across an interesting blog post .
The author states:
Redis is single-threaded with epoll/kqueue and scale indefinitely in terms of I/O concurrency.
I surely misunderstand the whole threading thing, because I find this statement puzzling. If a program is single-threaded, how does it do anything concurrently? Why it is so great that Redis operations are atomic, if the server is single-threaded anyway?
Could anybody please shed some light on the issue?