LLM Caching

Cut LLM costs and latency with exact match, semantic, and provider-side caching layers.

When to Use This Skill

Use this skill when:

• The same or similar queries are asked repeatedly (FAQ bots, support tools)
• LLM API costs are growing and you need immediate savings
• Serving high request volumes where repeated queries cause bottlenecks
• Implementing prompt caching for long system prompts (Anthropic/OpenAI)
• Building offline-capable AI features that need response persistence

Caching Layers

Request → Exact Cache → Semantic Cache → Provider Cache → LLM API
             ↓ hit            ↓ hit             ↓ hit
           instant          ~5ms           50-80% cheaper

Layer 1: Exact Match Cache (Redis)

import hashlib
import json
import redis
from openai import OpenAI

r = redis.Redis(host="localhost", port=6379, decode_responses=True)
client = OpenAI()

def build_cache_key(model: str, messages: list, temperature: float) -> str:
    """Deterministic key from request parameters."""
    payload = json.dumps({
        "model": model,
        "messages": messages,
        "temperature": temperature,
    }, sort_keys=True)
    return f"llm:exact:{hashlib.sha256(payload.encode()).hexdigest()}"

def cached_completion(model: str, messages: list, temperature: float = 0.0,
                      ttl: int = 3600) -> dict:
    key = build_cache_key(model, messages, temperature)

    # Check cache
    if cached := r.get(key):
        return json.loads(cached)

    # Call API
    response = client.chat.completions.create(
        model=model, messages=messages, temperature=temperature
    )
    result = response.model_dump()

    # Cache result (only cache deterministic responses)
    if temperature == 0.0:
        r.setex(key, ttl, json.dumps(result))

    return result

Layer 2: Semantic Cache (GPTCache)