Agree, that multi-threading probably the best choice for CPU-intensive applications. But for databases or http-servers multi-process + coroutines/fibers can be a better solution. For example, Redis is few-thread application. It creates additional threads only for disk I/O, because unfortunately file descriptors in Linux/UNIX do not work in async mode.

Btw, Redis reminds me, one really awesome usage of fork. To make a snapshot of itself Redis forks the main process. After that the child simply goes through tuples and write them to a files with out any worries that somebody will modify a records. Copy-on-write mechanism simply prevents it.

Redis save snapshot code: https://github.com/antirez/redis/blob/unstable/src/rdb.c#L99...