Hot vs. cold restarts
When rebooting an Umbraco CMS website it is common to distinguish between hot and cold restarts depending on your setup.
The load time of your site is dependent on a few different things. When talking about hot vs. cold restarts of your Umbraco CMS website it comes down to whether NuCache needs to be rebuilt.
Cold restart: When NuCache needs to rebuild.
Hot start: When NuCache does not need to rebuild.
Hot start
When no cache needs to be rebuild, the restart of your site is generally faster. This is why it is referred to as a hot restart.
Cold start
The cold restart expression is generally used for when the NuCache needs to rebuild. This will resolve in a slower startup time, depending on the amount of content on the site. Generally speaking, the more content you have the longer a cold boot will take.
Troubleshooting slow startup
Different things could be in play when your site is slow to startup after a reboot/restart.
Below is a list of some of the more common reasons:
NuCache needs to rebuild (cold restart).
Examine indexes need to rebuild - for large sites, this can take some time.
The custom code on the website is not optimized and does not live up to .NET standards.
In Memory Auto
This is, however, less noticeable on consecutive restarts, a bit like hot and cold restarts. Since the compiled models will be cached on disk, they don't need to be recompiled until the models change again.
Legacy Umbraco
In earlier versions of Umbraco, the difference between hot and cold restarts was more distinct as more components were involved with this process.
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