There's nothing about the code being slow in the example. The example said the processes were io bound. The speed of ruby code is irrelevant. If it was io bound

There's nothing about the code being slow in the example. The example said the processes were io bound. The speed of ruby code is irrelevant. If it was io bound demo system had 2 processes sitting 99% idle. The example said there was 0.5 seconds of IO per request so each process could serve 2 requests per second. 2 processes would serve 4 requests per second. The mistake was running only one process per core. 10 processes would server 40 requests per second, and the cores would still be mostly idle. With rails you always run as many processes as memory allows, not one per core. Now that rails is thread safe you can have each process run a few threads. If you ran 10 processes and 4 threads per process you are up to 120 requests per second. If you really need massive concurrency that isn't anything special. But that is more than enough for 90% of the web apps out there.