Provider prompt caches reuse computation
OpenAI, Anthropic, and Google document caching mechanisms for repeated prompt context. These features are useful when many calls share a long system prompt, document, tool schema, or conversation prefix. The model still handles the uncached portion and produces a new output.
Pricing, minimum token requirements, cache lifetime, and explicit versus automatic controls differ by provider. Use each provider's current documentation rather than assuming one cache policy applies everywhere.
Semantic response caches reuse answers
A gateway-level semantic cache stores a completed response and may return it for a later request. That can remove nearly the entire provider call, but the gateway must decide that the old response is still appropriate.
This works best for stable, repetitive questions with low personalization and low freshness sensitivity. It is a poor default for account state, current prices, legal or medical advice, or any answer that depends on live retrieval.
Use them together deliberately
A route can check an exact response cache, then a tightly scoped semantic cache, and finally call the provider with prompt caching enabled. Each layer needs separate telemetry so operators know which mechanism produced savings.
Do not label all three outcomes simply as a cache hit. A response reuse event carries different correctness and privacy implications from a discounted prefix.
- Exact response cache: highest confidence, narrow reuse
- Semantic response cache: broader reuse, requires evaluation
- Provider prompt cache: repeated prefix, new generation
- No cache: full input and generation
Compare effective cost, not feature checkboxes
Measure eligible traffic, actual hit rate, discount rate, added infrastructure, latency, invalidations, and failure cost. The best mix depends on prompt repetition and route risk, not on which vendor advertises caching most prominently.
Frequently asked questions
Does prompt caching return the same answer?
No. It reuses processing for cached input tokens, but the model generates a new continuation.
Can semantic caching use provider prompt caching?
Yes. If the semantic cache misses, the provider request can still benefit from a repeated-prefix cache.
Which cache should be implemented first?
Start with provider prompt caching and exact response caching. Add semantic response reuse only after route-specific false-hit testing.
Sources and further reading
FrugalAI uses primary documentation and published research where possible. Product capabilities and prices can change; verify vendor details before procurement or production changes.