Vercel's ISR Observability page now surfaces a write utilization metric for Observability Plus subscribers. The metric is a ratio of cached requests to ISR writes, exposing routes that regenerate frequently but serve few actual requests. That imbalance means you are paying for revalidation cycles that almost nobody sees.
Routes with low write utilization have two practical fixes: increase the revalidation interval or switch to on-demand revalidation. Both options reduce unnecessary ISR writes and cut costs. The metric is also accessible via the Vercel CLI and through agents using the cdn-caching skill, so investigation does not require the dashboard.
The article is worth reading in full for the cost-reduction guide linked directly from the changelog, which goes beyond the metric itself into concrete configuration changes. If ISR is a meaningful part of your architecture, the write utilization ratio gives you a number to optimize against, not just a vague sense that revalidation is expensive.
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