Do we need a widget cache?

[bobbingwide]

In seriouslybonkers.com I used to use oik-widget cache to cache the contents of the sidebar widgets.
But there was a probem with caching of the Sequentially Biased widget since it supports pagination;
see bobbingwide/oik-widget-cache#3

oik-widget-cache has been deactivated for a while, but I can't remember why I did it.

Anyway, now that the widgets are implemented as blocks I'm wondering if there's a server performance benefit to caching a selection of the widgets? ie. Can some of the template parts be cached?
If so, how do we go about doing it?

Possible solution

• Since we're already implementing override logic on template-parts we could implement a className attribute of "cache" on the template part. When this is detected then we'll look to see if there's a cached version.
• The logic should also take into account the fact that the template-part is newer than the cached version.
• If so, then it should use the new template part and re-cache the output.