Suppose a system without caching required 20 replicas, but with caching required only 15. If each replica is a machine, this means the cache is more cost-effective if it costs less than purchasing 5 machines.
This might be dangerous advice. It sounds like using cache as a scaling/availability strategy, which can be risky. Loss of cache means outage? Caching should be a performance tool, not availability tool.
What about p99/p100? We have situations where caching is the only thing keeping an API/page working. Otherwise, it's unavailable for a par…