llm-gateway

LLM Gateway

A unified API gateway that routes LLM requests across providers and self-hosted models — with rate limiting, cost tracking, caching, and failover.

When to Use This Skill

Use this skill when:

• Running multiple LLM backends (OpenAI, Anthropic, vLLM, Ollama) behind a single endpoint
• Enforcing per-team or per-user rate limits and spend budgets
• Implementing automatic fallback when a provider is down
• Adding semantic caching to reduce API costs by 20–50%
• Centralizing API key management instead of distributing keys to every app

Prerequisites

• Docker and Docker Compose
• A PostgreSQL or SQLite database (for LiteLLM state)
• LLM API keys (OpenAI, Anthropic, etc.) or self-hosted vLLM endpoints
• Optional: Redis for caching and rate limiting

LiteLLM Proxy — Quick Start

LiteLLM is the de facto open-source LLM gateway with OpenAI-compatible API.

# Run with Docker
docker run -d \
  --name litellm-proxy \
  -p 4000:4000 \
  -e OPENAI_API_KEY=$OPENAI_API_KEY \
  -e ANTHROPIC_API_KEY=$ANTHROPIC_API_KEY \
  -v $(pwd)/litellm-config.yaml:/app/config.yaml \
  ghcr.io/berriai/litellm:main-latest \
  --config /app/config.yaml \
  --detailed_debug

LiteLLM Configuration

# litellm-config.yaml
model_list:
  # OpenAI models
  - model_name: gpt-4o
    litellm_params:
      model: openai/gpt-4o
      api_key: os.environ/OPENAI_API_KEY
      rpm: 10000
      tpm: 2000000

  - model_name: gpt-4o-mini
    litellm_params:
      model: openai/gpt-4o-mini
      api_key: os.environ/OPENAI_API_KEY

  # Anthropic
  - model_name: claude-sonnet-4-6
    litellm_params:
      model: anthropic/claude-sonnet-4-6
      api_key: os.environ/ANTHROPIC_API_KEY

  # Self-hosted vLLM instances (load balanced)
  - model_name: llama-3.1-8b
    litellm_params:
      model: openai/meta-llama/Llama-3.1-8B-Instruct
      api_base: http://vllm-1:8000/v1
      api_key: fake                    # vLLM key
  - model_name: llama-3.1-8b
    litellm_params:
      model: openai/meta-llama/Llama-3.1-8B-Instruct
      api_base: http://vllm-2:8000/v1  # second replica — auto load balanced
      api_key: fake

  # Fallback: cheap model if primary fails
  - model_name: gpt-4o
    litellm_params:
      model: openai/gpt-4o-mini        # fallback to cheaper model
      api_key: os.environ/OPENAI_API_KEY

router_settings:
  routing_strategy: least-busy         # or: latency-based, simple-shuffle
  num_retries: 3
  retry_after: 5
  allowed_fails: 2
  cooldown_time: 60

  # Fallback configuration
  fallbacks:
    - gpt-4o: [claude-sonnet-4-6]
    - claude-sonnet-4-6: [gpt-4o]

litellm_settings:
  # Semantic caching
  cache: true
  cache_params:
    type: redis
    host: redis
    port: 6379
    similarity_threshold: 0.90        # cache if >90% semantic similarity

  # Logging
  success_callback: ["langfuse"]
  failure_callback: ["langfuse"]
  langfuse_public_key: os.environ/LANGFUSE_PUBLIC_KEY
  langfuse_secret_key: os.environ/LANGFUSE_SECRET_KEY

general_settings:
  master_key: os.environ/LITELLM_MASTER_KEY
  database_url: postgresql://litellm:password@postgres:5432/litellm
  store_model_in_db: true