DeepOffer

Explain prefix/prompt caching: when to use it and what invalidates a cached prefix.

ML System DesignReported interview question
Reported in public interview compilations — Moonshot AI, Character.AI

Prefix caching reuses KV states for identical prompt prefixes. It helps shared system prompts and repeated documents; any token, position, model version, adapter, or decoding context that changes the computed states invalidates the entry.

Make interfaces and ownership explicit; add versioning, access control, monitoring, canary rollout, rollback, and a plan for delayed labels or human review.

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