LLM Gateways & Routing
LLM Gateway Architecture
3 min read
LLM gateways provide a unified interface for managing multiple LLM providers, enabling routing, fallbacks, cost optimization, and observability from a single control point.
Why LLM Gateways?
Without Gateway: With Gateway:
───────────────── ────────────────
┌─────────────┐ ┌─────────────┐
│ Service A │───→ OpenAI │ Service A │─┐
└─────────────┘ └─────────────┘ │
│
┌─────────────┐ ┌─────────────┐ │ ┌─────────┐
│ Service B │───→ Anthropic │ Service B │─┼──→│ Gateway │───→ Providers
└─────────────┘ └─────────────┘ │ └─────────┘
│ │
┌─────────────┐ ┌─────────────┐ │ ┌───┴───┐
│ Service C │───→ Azure │ Service C │─┘ │OpenAI │
└─────────────┘ └─────────────┘ │Anthro │
│Azure │
Problems: Benefits: │Bedrock│
• N×M integrations • Single API └───────┘
• No unified monitoring • Central control
• Hard to switch providers • Easy fallbacks
• Scattered credentials • Unified logging
Gateway Features
┌─────────────────────────────────────────────────────────────┐
│ LLM Gateway Capabilities │
├─────────────────────────────────────────────────────────────┤
│ │
│ Routing & Load Balancing │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ • Model-based routing │ │
│ │ • Latency-based routing │ │
│ │ • Cost-based routing │ │
│ │ • Weighted distribution │ │
│ │ • Fallback chains │ │
│ └─────────────────────────────────────────────────────┘ │
│ │
│ Reliability │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ • Automatic retries with backoff │ │
│ │ • Fallback to alternative providers │ │
│ │ • Health checks and circuit breakers │ │
│ │ • Request queuing during outages │ │
│ └─────────────────────────────────────────────────────┘ │
│ │
│ Cost Management │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ • Budget limits per team/project │ │
│ │ • Rate limiting by user/API key │ │
│ │ • Spend tracking and alerts │ │
│ │ • Automatic model downgrade on budget │ │
│ └─────────────────────────────────────────────────────┘ │
│ │
│ Security & Governance │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ • Centralized credential management │ │
│ │ • Virtual API keys for teams │ │
│ │ • Request/response logging │ │
│ │ • PII detection and redaction │ │
│ └─────────────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────┘
Gateway Solutions Comparison
| Solution | Type | Best For | Key Features |
|---|---|---|---|
| LiteLLM | Open-source | Flexibility, self-host | 100+ providers, async, A2A |
| Helicone | SaaS/Self-host | Observability | 8ms latency, caching |
| Portkey | SaaS | Enterprise | Governance, security |
| Martian | SaaS | Routing optimization | Auto-routing |
| OpenRouter | SaaS | Simple access | Pay-per-use |
Common Architecture Patterns
Pattern 1: Central Gateway
┌──────────────────────────────────────────────────────────┐
│ Central Gateway │
├──────────────────────────────────────────────────────────┤
│ │
│ All services → Gateway → Providers │
│ │
│ Pros: Cons: │
│ • Single point of control • Single point of failure │
│ • Easy management • Latency added │
│ • Unified logging • Scaling complexity │
│ │
└──────────────────────────────────────────────────────────┘
Pattern 2: Sidecar Gateway
┌──────────────────────────────────────────────────────────┐
│ Sidecar Gateway │
├──────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────────────┐ │
│ │ Pod │ │
│ │ ┌────────┐ ┌─────┐│ │
│ │ │ Service│→│Sidecar│→ Providers │
│ │ └────────┘ └─────┘│ │
│ └─────────────────────┘ │
│ │
│ Pros: Cons: │
│ • No network hop • Per-pod resource usage │
│ • Local caching • Configuration sprawl │
│ • Service isolation • Complex updates │
│ │
└──────────────────────────────────────────────────────────┘
Pattern 3: Hybrid (Recommended)
┌──────────────────────────────────────────────────────────┐
│ Hybrid Pattern │
├──────────────────────────────────────────────────────────┤
│ │
│ SDK (client-side) + Central Gateway (server-side) │
│ │
│ ┌────────────┐ │
│ │ Service │ │
│ │ ┌───────┐ │ ┌─────────┐ │
│ │ │LiteLLM│──────→│ Gateway │──→ Providers │
│ │ │ SDK │ │ │(routing)│ │
│ │ └───────┘ │ └─────────┘ │
│ └────────────┘ │
│ │
│ SDK handles: retries, formatting, streaming │
│ Gateway handles: routing, budgets, logging │
│ │
└──────────────────────────────────────────────────────────┘
Key Considerations
- Latency: Gateway adds 1-10ms overhead; acceptable for most LLM calls (100ms+)
- Reliability: Gateway should be highly available; consider multi-region
- Caching: Gateway can cache identical requests for significant cost savings
- Compliance: Central logging helps with audit requirements
- Team Access: Virtual keys enable per-team quotas and tracking :::