Originally in #1494 (comment).

I discovered on my blog that I had a very old URL Metric from before the XPath indices were fixed to be 1-based instead of 0-based (#1191). Looking at the URL Metric data, I see the timestamp is 1712354502.752218 which is for a day back in April. It appears that URL Metrics are not being collected frequently enough, or my site is truly devoid of traffic. I think for my site it may be in part due to page caching, where the detection time window (od_detection_time_window) is too short, so it is only collecting metrics for visitors who happen to visit when there is a MISS to the page cache, and if there is a stale-while-revalidate caching strategy going on with Varnish then it is even more likely for the visitor to never be within the detection time window (currentTime - serveTime > detectionTimeWindow):

I think this logic needs to be revisited.