The idea comes form a support case: SUPPORT-5122

When using the strategy "Serving from old cache":
After the cache flush, the first hit of a page is served form new cache which triggers the re-rendering and re-aching.
All others get served from the old cache until the new entry is there.

Now an idea, inspired by the "'Eager re-caching" strategy:
Serve also the first visitor from the old cache, and trigger the re-rendering and re-caching in the back-end decoupled.

So everybody gets all the time fast responses, instead of having a first visitor waiting.