# Amazon SageMaker Adds Prefix-Aware Routing to Cut LLM Latency

Digest AI · Enterprise & Industry · published 2026-09-10T21:58:09Z

Canonical: https://digestai.news/story/amazon-sagemaker-adds-prefix-aware-routing-to-cut-llm-latency

## Summary

Amazon SageMaker Inference now supports prefix‑aware routing, a strategy that sends requests with identical prompt beginnings to the same instance. By keeping the key‑value cache warm, the feature cuts the time‑to‑first‑token (TTFT) for Llama 3.1 70B by up to 77 % and boosts throughput by roughly 16 %. The technique also raises cache hit rates from about 25 % to over 80 %, with only a 1.3–1.9 ms routing overhead per request.

The new routing mode is ideal for workloads that share long prefixes, such as retrieval‑augmented generation, multi‑turn conversations, templated bots, and code‑completion tools. It works with popular serving frameworks like vLLM and TensorRT‑LLM, and can be enabled via the endpoint configuration without modifying the model container.

Users can tune the strategy with PrefixLength and ConcurrencyThreshold parameters, and the system automatically balances traffic and protects against overload. The feature is available today on SageMaker real‑time inference endpoints and requires only an updated SDK or CLI.

## Key points

- Prefix‑aware routing sends identical prompt prefixes to the same instance, boosting cache reuse.
- Benchmarks on Llama 3.1 70B show up to 77 % TTFT reduction and 16 % throughput increase.
- The feature adds only 1.3–1.9 ms per request and works with vLLM/TensorRT‑LLM without container changes.

## Why it matters

It dramatically lowers inference latency for LLM workloads, enabling faster, more cost‑effective deployments at scale.

## Sources

1. [Reduce LLM latency with prefix-aware routing on Amazon SageMaker Inference](https://aws.amazon.com/blogs/machine-learning/reduce-llm-latency-with-prefix-aware-routing-on-amazon-sagemaker-inference) (AWS Machine Learning Blog, 2026-09-10, primary source)

Part of the developing story: [AWS Optimizes Enterprise AI Infrastructure](https://digestai.news/thread/amazon-sagemaker-hyperpod-introduces-model-caching-to-cut-cold-starts) (10 stories)

## Cite

Digest AI, "Amazon SageMaker Adds Prefix-Aware Routing to Cut LLM Latency", 10 September 2026, https://digestai.news/story/amazon-sagemaker-adds-prefix-aware-routing-to-cut-llm-latency

---

Written by Digest AI's editorial model from the linked sources; the sources are the record. Headlines, digests and key points are written by Digest AI and may be quoted with a link to the story page. Linked articles belong to their publishers. Terms: https://digestai.news/terms#reuse
JSON: https://digestai.news/story/amazon-sagemaker-adds-prefix-aware-routing-to-cut-llm-latency.json