API Gateways for LLM Traffic

A company calling five different LLM providers, OpenAI, Anthropic, Google, Cohere, and a self-hosted open-source model, directly from application code ends up with five different rate limit schemes, five different pricing models, and five different failure modes scattered across the codebase. An LLM gateway exists to absorb all of that into one place, so the application only ever talks to one consistent interface.

• -Unified interface: one API shape regardless of which provider actually serves the request underneath.
• -Cost-based routing: send each request to the cheapest currently healthy provider, automatically.
• -Failover: if the chosen provider is down or erroring, retry on the next one without the caller ever noticing.
• -Rate limiting: enforced consistently per user or per tenant, regardless of which provider ends up serving the request.

A gateway is only as good as how quickly it notices a provider is unhealthy. Checking every 15 seconds or faster keeps the window where the gateway is still confidently routing to a dead provider short. This connects directly forward to the disaster recovery chapter later in this tier, where health-check interval becomes the actual unit that failover time is measured in.