Latency numbers worth memorising

The orders of magnitude, not the digits:

The useful consequence: one network call costs as much as a million memory accesses, so batching calls beats optimising the code between them.

Classic signature of a cache that misses under load: every miss now pays the lookup plus the original work, and the population step often serialises on a lock. Measure hit rate before and after, and add jitter to expiry so entries do not all die in the same second.