System start is indeed a synchronization point, and for limited resources like here, painful and now clpser to the vernacular

Thundering herds can cause escalating and successive failures. That is very much an issue with service start/restart. A bad restart will cause a timeout, another restart, and eventually, restarts on further layers. Imagine all this running above k8s. So yes, this pattern is indeed about one of the failure modes that happen with thundering herds.

Though if your cache needs another cache, that feels like a bad cache. The promise pattern can be done transparently by the cache, coalescing GETs, instead of requiring a user protocol. We do app level caching to stay process-local because latency is fun in GPU land and we are a visual analytics tool... But that is not for the problem shown here.