Each Sitecore site contains its own HTML cache; its full utilization is really necessary to improve website performance. On each publish, Sitecore clears the HTML cache on the CD server of all the sites specified in the publish:end:remote
event's HtmlCacheClearer
handler as follows:
It is not a good practice that we clear the cache of all sites when publishing happens for a single site item as this can impact the performance of all the sites, and after this, each site will go to build an HTML cache again. This becomes critical when we have a large number of sites and publishing happens very frequently.
This recipe will explain how we can clear a site-specific HTML cache based on items that got published. This recipe will be very useful to improve the performance of sites when there are multiple sites hosted on a single Sitecore instance.