Llm Gateway Cost And Caching easy
You have budget to add a semantic cache to one of two features: a help-center FAQ bot and a marketing slogan generator. Where will it pay off?
- A On the slogan generator, since users submit many similar prompts for taglines.
- B On the FAQ bot, where many users ask near-identical questions with stable answers.
- C On both features equally, since embedding similarity works the same for any task.
- D On neither, since semantic caches only match prompts that are character-identical.
Answer: B. On the FAQ bot, where many users ask near-identical questions with stable answers.
FAQ-like traffic often reaches **20% to 40% hit rates** because questions repeat and answers rarely change. Creative tasks see near-zero useful hits: users want new output each time, so returning a cached slogan defeats the feature. The tradeoff is savings versus answer variety; exact character matching describes exact-match caching, not semantic caching.
One system design question a day, with spaced repetition so the ones you miss come back.
Get the appRelated questions
- Your primary LLM provider is fully down for an hour, and no tested fallback exists for your agent feature. The product also has an FAQ answer feature backed by a semantic cache. What is the best degradation mode?
- Your gateway applies one 5-second timeout to all LLM calls. Classification calls work fine, but long streamed answers are frequently cut off. What is the best fix?
- A multi-tenant B2B support assistant answers questions using each customer's private knowledge base. To raise the semantic cache hit rate from 22% to 35%, an engineer proposes one shared cache across all tenants. What is the main problem?
- During a provider brownout returning 429 and 503 errors, the client SDK retries 3 times and the gateway also retries 3 times, both immediately. Provider load spikes, and the bill grows from partially streamed responses. What should you change?
- Finance asks for LLM spend broken down by tenant and by product feature. Today the gateway only sees the total on the provider's monthly invoice. What should you do?
- A retail assistant uses a semantic cache. Weeks after a store changed its holiday hours, users still receive the old hours from cached answers. What is the right fix?