As far as Core, I believe, but I’m not 100% sure, that it can also receive an HTTP post. So that might run a little faster than doing the same thing through IFTTT. But ask in the core peer assistance thread and someone there should know.
With regards to IFTTT, it varies from house to house and applet to applet, although it has gotten somewhat faster than it was about a year ago. At my house, it’s a fairly consistent eight second delay, which is sufficient for many purposes, but not all. You may just have to try it and see.