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Building a Production-Grade AI Gateway on AWS: Token-Aware Rate Limiting, Semantic Caching, Model Routing & Cost Observability

AI gateways need to manage more than API requests. This article builds a production-oriented architecture for token-aware rate limiting, semantic caching, model routing, streaming cost tracking, and per-application observability using FastAPI, Redis, and Amazon Bedrock.

Building a Production-Grade AI Gateway on AWS: Token-Aware Rate Limiting, Semantic Caching, Model Routing & Cost Observability

Modern AI applications rarely depend on a single LLM request.
As traffic grows, teams have to answer harder questions:
  • Who is consuming the most tokens?
  • What happens when token quotas are exhausted?
  • Can repeated questions avoid another model call?
  • Should every request use the most expensive model?
  • What happens when a user cancels a streaming response?
  • Can we trace one request across the gateway, cache, model and logs?
An API gateway that only forwards requests is not enough.
A production AI gateway needs to become an intelligent control plane between applications and foundation models.
In this article, I’ll extend a basic FastAPI + Redis LLM gateway into a production-oriented architecture with:
  • Token-aware rate limiting
  • Redis-backed reservation and settlement
  • Semantic response caching
  • Model routing and fallback
  • Streaming-aware cost tracking
  • Per-user and per-application cost attribution
  • Request correlation and observability
  • Amazon Bedrock integration

1. The Problem With Request-Based Rate Limiting

A common implementation looks like:
Client → API Gateway → Redis → LLM
and limits requests such as:
1
100 requests / minute
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