Caching and Batching for LLM Cost Savings
Learn how response caching, prompt caching, and request batching dramatically cut LLM cost and latency in production applications.
Caching and Batching for LLM Cost Savings is a free Prompt Engineering & LLM Optimization for Developers lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Prompt Engineering & LLM Optimization for Developers learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Cost Adds Up Fast
Every LLM call costs tokens for both input and output. At scale, repeated and redundant calls quietly dominate your bill. Caching and batching are the two biggest levers to cut cost without hurting quality.
Exact-Match Response Caching
If the same prompt is sent again, return the stored answer instead of calling the model. Use a hash of the full prompt as the cache key.
const key = hash(prompt);
if (cache.has(key)) return cache.get(key);
const out = await llm(prompt);
cache.set(key, out);When Exact Caching Works
Exact-match caching shines for deterministic, repeated queries: FAQ answers, classification of identical inputs, or cached embeddings. Set temperature: 0 so the same input reliably maps to the same output.
Semantic Caching
Many questions mean the same thing in different words. Semantic caching embeds the query and returns a cached answer if a previous query is close enough in vector space.
const v = embed(query);
const hit = vectorCache.nearest(v, threshold=0.95);
if (hit) return hit.answer;Provider Prompt Caching
Major providers offer prompt caching: a large, stable prefix (system prompt, docs) is cached on their side, so repeat calls only pay full price for the changing part. This can cut input cost by most of the prefix.
Structuring for Prompt Caching
Put the stable content first (instructions, reference docs) and the variable user input last. Cache hits depend on an identical prefix, so order matters.
[ system + docs (cached prefix) ]
[ user question (varies) ]The Batch API
For non-urgent jobs, providers offer a batch API that processes many requests asynchronously at roughly half price. Great for offline tasks like summarizing a backlog.
Micro-Batching Live Requests
Even for live traffic you can group requests that arrive within a short window into one call, amortizing fixed overhead. Balance the wait against added latency.
// collect requests for 50ms, then send together
flushAfter(50, pending);Cache Invalidation
Stale answers are dangerous. Invalidate cached responses when the underlying data or prompt template changes, and set a TTL for anything time-sensitive.
cache.set(key, out, { ttlSeconds: 3600 });Measuring Savings
Track cache hit rate and cost per request. A 40% hit rate cuts roughly 40% of those calls. Without measurement you cannot tell if caching is helping.
Combining the Techniques
- Exact cache for identical prompts.
- Semantic cache for paraphrases.
- Prompt caching for stable prefixes.
- Batch API for offline jobs.
Layered together they slash both cost and latency.
Quick Check
Test your understanding of LLM cost optimization.
Recap
Cut LLM cost with exact and semantic response caching, provider prompt caching of stable prefixes, and the batch API for offline work. Order prompts for cache hits, invalidate stale entries, and measure your hit rate.
Frequently asked questions
Is the “Caching and Batching for LLM Cost Savings” lesson free?
Yes — the full text of “Caching and Batching for LLM Cost Savings” is free to read here on the web, and the Prompt Engineering & LLM Optimization for Developers course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Prompt Engineering & LLM Optimization for Developers course, upgrade to CoddyKit PRO.
What will I learn in “Caching and Batching for LLM Cost Savings”?
Learn how response caching, prompt caching, and request batching dramatically cut LLM cost and latency in production applications. You practise Prompt Engineering & LLM Optimization for Developers with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Prompt Engineering & LLM Optimization for Developers?
No prior experience is required. Prompt Engineering & LLM Optimization for Developers on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Caching and Batching for LLM Cost Savings” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Prompt Engineering & LLM Optimization for Developers lesson?
Yes. Every Prompt Engineering & LLM Optimization for Developers lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Token Efficiency & Context Management
- Latency Reduction Techniques
- Output Parsing & Validation
- Caching and Batching for LLM Cost Savings