Hi Stan,

"requestDelay" attribute defines time interval during which components are allowed to wait for the new events. Example:

<a4j:commandLink requestDelay="1500" value="Link" />

Let current time be t:

t=0, link is clicked by the user, timer T1 started for 1500 (request delay, in ms) interval

t=1000, link is clicked by the user again, timer T1 is stopped and new timer T2 with the same interval is started

t=2500, link fires request by T2 timer expiration event

For the components in queues situation is slightly different because requests from another components force waiting ones to end wait and submit immediately - that's necessary to preserve events ordering.