การแคชและการเพิ่มประสิทธิภาพต้นทุนสำหรับแอป LLM

At scale, LLM API bills grow fast — you pay per input and output token on every call. Smart caching and routing can cut costs by an order of magnitude with no quality loss.

The simplest win: cache the full response keyed by the exact prompt. Identical requests return instantly and free.

Many prompts differ only in wording. A semantic cache embeds the query and returns a cached answer when a previous query is close enough in vector space.

Providers can cache a long, repeated prompt prefix (system instructions, few-shot examples). Reused prefixes are billed at a steep discount, saving tokens on every call.

Every token costs money. Remove redundant instructions, compress few-shot examples, and summarize long histories instead of sending the full transcript.

Do not use your most expensive model for everything. Route easy requests to a small cheap model and escalate only hard ones to a large model.

Some providers offer a batch API at a large discount for non-urgent jobs (overnight analytics, bulk classification). Trade latency for cost.

Output tokens are usually the priciest. Set max_tokens to the smallest value that still answers the question to avoid paying for rambling.

Streaming does not reduce cost but improves perceived latency, letting you use a slightly larger model without users feeling the wait.

You cannot optimize what you do not measure. Log tokens, latency, and cost per request and per feature so you know where the spend actually goes.

Caches can serve stale answers. Add a TTL, and bust cache entries when the underlying data, prompt template, or model version changes.

You learned to cut LLM cost and latency: exact-match and semantic caches, prompt-prefix caching, trimming prompts, model routing, batching, capping output tokens, and rigorous per-request cost monitoring with proper cache invalidation.