GenAI interview guides / Prefix Caching Interview Guide
Prefix Caching Interview Guide
Use prefix caching to skip repeated prompt prefill while reasoning about privacy, cache keys, and hit rate.
What is reused
Shared token prefixes can reuse KV states, reducing repeated prefill work.
Good workloads
Repeated system prompts, shared documents, few-shot exemplars, multi-turn history, and tool catalogs can produce strong reuse.
Design details
Prompt serialization, cache hashing, eviction, invalidation, and tenant isolation determine correctness and hit rate.
Security
Cross-tenant reuse or weak cache keys can create information-leak risks.