Semantic Cache Verification Measured: 30-40ms on the Hot Path vs 1.7s for an LLM Judge

Reasonable_Royal_621 · reddit · 2026-09-09

The author open-sourced CacheVerifier, which double-checks borderline semantic-cache hits, and published real latency numbers: with a lightweight scoring model on a 2 vCPU box, the check adds 30ms p50 / 44ms p95 server-side, and a real US-East client sees a nearly identical 33.5ms average round trip. Swapping in an async LLM judge changes everything: 1.7s average, with network handshakes alone eating up to half a second. The check only fires on borderline hits — roughly a quarter to half of traffic depending on threshold — so the tradeoff is whether a 30-40ms tax on the 'free' fast path is worth catching bad hits before they become support tickets. Full writeup in section 5.5 of the repo's PAPER.md, also published as a standalone paper.

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