Hi @davidfekke
As others have pointed out, publish is rate-limited to an average once per second with a burst of four allowed.
Variables and functions are not rate-limited but in my experience somewhere around once per second from a Javascript web page is about all I can get to work reliably. If you look for my tutorial with a servo you will see that since I am about 125ms from the cloud, the best case I could possibly achieve would be a 250ms round-trip time and a realistic time including all overhead is about once per second.
Alternatives include you own local Particle cloud or straight TCP or UDP.