ReferenceGlossary
Cache hit rate
The share of lookups that a cache answers from its own copy, without asking the slower system behind it. A miss goes to the origin or database. A small change in hit rate can change the load on the origin a lot: going from 90% to 80% doubles the misses.
Performance
In Quorum#
A Cache or CDN Node shows its hit ratio on its card. A Cache's hit rate is the square root of (its memory / hot data, about 200 KB per user) × a TTL factor (60% at 10 s, 85% at 60 s, 97% at 1 h) × a write penalty of up to 50% × how warm it is. A CDN answers 70% of page and 75% of media requests at the 300 s TTL, × 0.8 at 60 s or × 1.2 at 1 h, at most 95%. Give the Cache more memory or a longer TTL to raise the rate, but a longer TTL serves more stale reads.