Pegaflow

KV cache on the wings of Pegasus.

PegaFlow is a high-performance KV cache storage engine for LLM inference. Offload KV cache from GPU to host memory or SSD, and share it across nodes via RDMA.

• Decoupled from inference lifecycle — runs as an independent sidecar; KV cache survives engine restarts, scales independently, and is shared across instances
• Topology-aware, PCIe-saturating transfers — NUMA-aware pinned memory + layer-wise DMA to maximize hardware bandwidth
• GIL-free Rust core — zero Python overhead on the hot path; your inference engine keeps its threads
• Production-ready observability — built-in Prometheus metrics and OTLP export, not an afterthought
• Pluggable — works with vLLM as a drop-in KV connector

News

• 2026-05-18 — vLLM x Novita AI: PegaFlow for Production-Grade External KV Cache, a joint blog post with the vLLM team.

Architecture

Framework Integration

Framework	Status	Link
vLLM	✅ Ready	Quick Start

Quick Start

1. Install

uv pip install pegaflow-llm        # CUDA 12
uv pip install pegaflow-llm-cu13   # CUDA 13

2. Start PegaFlow Server

pegaflow-server

3. Launch your inference engine

vLLM:

vllm serve Qwen/Qwen3-0.6B \
  --kv-transfer-config '{"kv_connector": "PegaKVConnector", "kv_role": "kv_both", "kv_connector_module_path": "pegaflow.connector"}'

For full server options, multi-node setup, and advanced configuration, see Server Configuration.

Development

Build from source

export PYO3_PYTHON=$(which python)
export LD_LIBRARY_PATH=$(python -c "import sysconfig; print(sysconfig.get_config_var('LIBDIR'))"):$LD_LIBRARY_PATH

cargo run -r                    # start server
cd python && maturin develop -r # build Python bindings

The default source build targets CUDA 12.8. If your environment uses CUDA 13, disable the default CUDA feature and enable cuda-13 explicitly:

cargo run -r --no-default-features --features cuda-13 --bin pegaflow-server
cd python && uv run maturin develop -r --no-default-features --features cuda-13
./scripts/build-wheel.sh --release --no-default-features --features cuda-13

We use Conventional Commits — run cz c for an interactive commit prompt.

Benchmarks

KV Cache Benchmark

H800 reference numbers with Llama-3.1-8B (8 prompts, 10K-token prefill, 1-token decode, 4.0 req/s):

Configuration	TTFT mean (ms)	TTFT p99 (ms)
PegaFlow (Cold)	572.5	1113.7
PegaFlow (Warm)	61.5	77.0

The warm-start path achieves ~9x faster TTFT compared to cold-start, demonstrating effective KV cache sharing across requests.

Documentation

• Server Configuration — full CLI options, SSD cache, multi-node setup
• Python Package — Python bindings and vLLM connector configuration
• P2P KV Cache Sharing — cross-node RDMA setup, tuning, and troubleshooting
• P/D Router — prefill/decode disaggregation
• vLLM I/O Patch — optional patch for better transfer throughput
• Metrics — Prometheus and OTLP metrics reference
• Goals & Non-Goals — project scope and design philosophy