STALE - the path is in the cache but exceeded the revalidate time so it will be updated in the background
HIT - the path is in the cache and has not exceeded the revalidate time
The expiration (or rather Max Age) is defined by either the minimumCacheTTL configuration or the upstream image Cache-Control header, whichever is larger. Specifically, the max-age value of the Cache-Control header is used. If both s-maxage and max-age are found, then s-maxage is preferred. The max-age is also passed-through to any downstream clients including CDNs and browsers.
You can configure minimumCacheTTL to increase the cache duration when the upstream image does not include Cache-Control header or the value is very low.
You can configure deviceSizes and imageSizes to reduce the total number of possible generated images.
You can configure formats to disable multiple formats in favor of a single image format.
minimumCacheTTL