llm-d is built for distributed LLM serving: routing, flow control, placement, auto-scaling, disaggregation decisions, engine configuration, all happening at once. That makes it powerful, but also hard to evolve. A small policy change in admission, routing, batching, or autoscaling can change latency, throughput, and inference cost in unexpected ways.

The only honest way to know is to test. But testing every idea on real GPU clusters is slow and expensive.

BLIS solves this problem.

The Problem with "Simple" LLM Deployments​

Everyone is racing to run Large Language Models (LLMs), in the cloud, on-prem, and even on edge devices. The real challenge, however, isn't the first deployment; it's scaling, managing, and maintaining hundreds of LLMs efficiently. We initially approached this challenge with a straightforward vLLM deployment wrapped in a Kubernetes StatefulSet.

Not all LLM requests cost the same. A short prompt might complete in milliseconds, while a long one can occupy a GPU for seconds. If we can predict how long a request will take on each candidate server before dispatching it, we can make substantially better routing decisions. This post describes a system that does exactly that: a lightweight ML model trained online from live traffic that replaces manually tuned heuristic weights with direct latency predictions.

llm-d is a distributed inference platform spanning multiple vLLM instances. KV cache hits are critical to achieving high inference throughput. Yet, in a distributed environment, cache hits do not occur across different nodes as the KV cache is local to each vLLM instance. In addition, this local cache is limited in size, further limiting KV data reuse. This blog presents a new way to offload KV cache to storage, tackling both aforementioned challenges – KV cache sharing and KV cache scale. llm-d's filesystem (FS) backend is a KV cache storage connector for vLLM that offloads KV blocks to shared storage based on vLLM's native Offloading Connector. While the llm-d FS backend can speed up serving of single requests (improve TTFT), its main goal is rather to preserve stable throughput and low latency at scale, as concurrency and context lengths grow. This is accomplished by significantly enlarging the cache space and enabling KV reuse across multiple replicas and nodes in llm-d.

While there are a number of existing solutions for KV cache offload to storage (e.g. LMCache or Dynamo KVBM), the new connector offers simplicity, can run with llm-d and vLLM as the only dependency, and exhibits improved performance over state-of-the-art shared storage connectors.

In our previous release (v0.4), we focused on improving the end-to-end latency of production inference, introducing speculative decoding and extending prefill/decode disaggregation across a broader set of accelerator architectures. That work established llm-d’s ability to deliver state-of-the-art latency along the critical serving path. Sustaining low latency increasingly depended on how KV-cache pressure is handled once GPU memory is saturated, whether cached state can be reused across replicas instead of being repeatedly rebuilt, and how requests are routed when workloads mix adapters, models, and availability requirements.

With v0.5, llm-d expands its focus from peak performance to the operational rigor required to sustain performance at scale. This release prioritizes reproducibility, resilience, and cost efficiency, with concrete improvements across the following areas:

1. Developer Experience and reproducibility: We have simplified the benchmarking workflow with dedicated, in-guide benchmark support, allowing users to validate each “well-lit path” with a single command.
2. Hierarchical KV Offloading: A new storage architecture decouples cache capacity from GPU memory through native CPU and filesystem tiers.
3. Advanced Scheduling: Cache-aware routing now supports LoRA adapters and active-active high availability.
4. Resilient Networking: A new transport backend (UCCL) improves stability in congested networks.
5. Autoscaling Updates: We have introduced scale-to-zero capabilities for cost-efficient intermittent workloads.

llm-d’s mission is to provide the fastest time to SOTA inference performance across any accelerator and cloud. In our 0.3 release we enabled wide expert parallelism for large mixture-of-expert models to provide extremely high output token throughput - a key enabler for reinforcement learning - and we added preliminary support for multiple non-GPU accelerator families.

This release brings the complement to expert parallelism throughput: improving end-to-end request latency of production serving. We reduce DeepSeek per token latency up to 50% with speculative decoding and vLLM optimizations for latency critical workloads. We add dynamic disaggregated serving support to Google TPU and Intel XPU to further reduce time to first token latency when traffic is unpredictable, while our new well-lit path for prefix cache offloading helps you leverage CPU memory and high performance remote storage to increase hit rates and reduce tail latency. For users with multiple model deployments our workload autoscaler preview takes real-time server capacity and traffic into account to reduce the amount of time a model deployment is queuing requests - lessening the operational toil running multiple models over constrained accelerator capacity.

These OSS inference stack optimizations, surfaced through our well-lit paths, ensure you reach SOTA latency on frontier OSS models in real world scenarios.

In our 0.2 release, we introduced the first well-lit paths, tested blueprints for scaling inference on Kubernetes. With our 0.3 release, we double down on the mission: to provide a fast path to deploying high performance, hardware-agnostic, easy to operationalize, at scale inference.

This release delivers:

• Expanded hardware support, now including Google TPU and Intel support
• TCP and RDMA over RoCE validated for disaggregation
• A predicted latency based balancing preview that improves P90 latency by up to 3x in long-prefill workloads
• Wide expert parallel (EP) scaling to 2.2k tokens per second per H200 GPU
• The GA release of the Inference Gateway (IGW v1.0).

Taken together, these results redefine the operating envelope for inference. llm-d enables clusters to run hotter before scaling out, extracting more value from each GPU, and still meet strict latency objectives. The result is a control plane built not just for speed, but for predictable, cost-efficient scale.

The llm-d project provides a series of “well-lit paths” - tested, benchmarked solutions for deploying large language models in production. Our first path, Intelligent Inference Scheduling, established a baseline for AI-aware routing by balancing both cluster load and prefix-cache affinities. The default configuration for that path uses an approximate method for the latter, predicting cache locality based on request traffic.

This blog illuminates a more advanced and powerful path: precise prefix-cache aware scheduling.

We take a deep dive into the next generation of this feature, which moves beyond prediction and gives the scheduler direct introspection into distributed vLLM caches. This precision is key to maximizing cache hit rates and achieving a new level of performance and maximizing cost-efficiency in your distributed deployments.

The llm-d project lays out clear, “well-lit” paths for anyone to adopt the leading inference optimizations within their existing deployment framework - Kubernetes. These are tested approaches designed to make complex deployments easier and more efficient. In this post, we explore the first of these paths: intelligent inference scheduling. Unlike basic round-robin load balancing, this method takes the unique demands of LLMs into account, leading to better performance across the board: higher throughput, lower latency, and efficient use of resources.

Why Intelligent Inference Is Needed for LLM Inference​

Deploying large language models (LLMs) on Kubernetes has become the norm, but LLM inference workloads behave very differently from standard microservices. Traditional patterns like uniform replicas paired with round-robin load balancing assume each request uses the same amount of resources and finishes in roughly the same time. In contrast, LLM requests can vary wildly in token count and compute needs, making simple load-spread strategies prone to bottlenecks and imbalanced traffic.

Our 0.2 release delivers progress against our three well-lit paths to accelerate deploying large scale inference on Kubernetes - better load balancing, lower latency with disaggregation, and native vLLM support for very large Mixture of Expert models like DeepSeek-R1.

We’ve also enhanced our deployment and benchmarking tooling, incorporating lessons from real-world infrastructure deployments and addressing key antipatterns. This release gives llm-d users, contributors, researchers, and operators, clearer guides for efficient use in tested, reproducible scenarios.