New Relic reporting seems to show a strong correlation between the previewEntry method's transactions and a couple of recent apdex-based alerts (the periods indicated by the pink background):
(The third period of previewing shown near the end of the chart is my failed attempt to trigger an alert; perhaps my test entry was less intensive than the client's.)
To cut down on the number of previews generated, how can I set a minimum interval between preview update POSTs, such as five seconds?
Update: we think it likely that the alert from New Relic was not actually a problem in terms of performance, and that it's simply a case of all/most of the requests during those periods taking longer than usual. It's a relatively quiet site, and so the live preview POST requests can easily represent 100% of requests. So I'm not so worried about this now, but it might still be nice to be able to set a minimum interval between live updates when the live update feature has been activated.
