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Semantic Caching for LLM Applications (ANSWERED)

Project BasedLLMsMedium15 min read

Project question on semantic cache — embedding similarity hits, TTL, invalidation, and staleness risks.

TL;DR — Quick Answer

Semantic cache stores prior query embeddings and responses; new queries embed and hit cache if cosine similarity exceeds threshold — catches paraphrases exact match misses. Differs from prompt/KV cache (identical prefix) and HTTP cache (exact key). Risks: stale answers after KB update, false positives merging distinct intents, privacy (user A sees cached B answer). Mitigate with TTL, knowledge version tags in cache key, threshold tuning on eval, and never cache personalized/account-specific answers without user scoping in key.

The Interview Question

What is semantic caching for LLM apps and how does it differ from exact prompt caching?

Deep Explanation

Exact vs semantic cache

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Semantic CacheCachingEmbeddingsCostLatencyOpenAIRedisPinecone