For each menu, wordpress reads data from the database and elaborated the results. This process, repeated at each page view, is a waste time and resource.
This plugin offers a caching solution that reduces this effects on performance.
The only downside is that the menu will not show the active item with a different style. This plugin cache one version of the menu for all pages.
Configurations are not required! You just have to install it and after the plugin does it all, none further action it’s required.
This plugin is very light: only 5 kb.
If you are using user-specific dynamic menu items, this plugin will break that functionality, as it will cache the state of the first page load and any changes will not be seen. There is no per-user cache.