Computer networking primer - HTML5 in Action - page 496

Figure D.4. The worst cases for polling: top—when new data is available far more frequently than it's polled for;
bottom—when polling happens far more frequently than there's data available.
The solution is to switch from polling to event-driven communication, as illustrated in fig-
ure D.5 . Then the server, which knows when the information is available, is in charge of
when information is delivered.