If this is really a Pri-1, find an owner and update the priority.

This is the result of a bulk edit that moved high priority available bugs to a lower priority in an attempt to be more honest with bug filers.

Not fixed yet :( Needs to be deployed to other luci-config-consuming services. Off the top of my head:
- Milo
- Scheduler
- Dungeon Master

Deployment is easy:
- Add a cron task: https://github.com/luci/luci-go/blob/211540cd92322bcc7bc5e44791ff51ef0f07c5f7/appengine/gaemiddleware/resources.cfg#L10
- Go to /admin/settings/gaeconfig and set "Enable datastore-backed caching" to Enabled (works, but cache fail will fall through) or Strict (works, and any cache fail will be an error).

luci-logdog production is set to "Strict" FWIW.

There we go.

Scheduler doesn't need it. It calls luci-config from cron already. Adding one more layer of crons and caching will just complicate data flow.

Same for Token Server.

In both cases crons do some postprocessing of configs and store the result in datastore in a form suitable for fast consumption, so even if luci-config cached existed before, I'd still had separate cron to handle configs.

this feature is implemented. Its adoption in concrete apps is outside of the scope