vLLM is a high-throughput, memory-efficient inference and serving engine for large language models (LLMs). It implements PagedAttention for near-zero waste KV cache management, continuous batching, chunked prefill, prefix caching, CUDA/HIP graphs, speculative decoding, and torch.compile. The system serves OpenAI-compatible APIs (chat completions, completions, embeddings, rerank, speech-to-text), Anthropic Messages API, Cohere API, and custom pooling/classification endpoints. It supports 200+ model architectures including dense, MoE, hybrid SSM/attention, and multimodal models (vision, audio, video). The architecture is a hybrid Python/Rust system: a Python core handles model execution, scheduling, and kernel dispatch, while a Rust frontend provides a high-performance HTTP/gRPC server with middleware for auth, metrics, and load management. Key entry points include the `vllm` CLI (serve, bench, launch), the `LLM` class for offline inference, and the OpenAI-compatible API server. External dependencies include PyTorch, HuggingFace Transformers, FlashAttention, CUTLASS, Triton, NCCL/RCCL, and various quantization libraries. The project is production-grade with extensive CI/CD, Docker images, Helm charts, and deployment integrations for Kubernetes, Ray, SageMaker, and more.
SGLang is a high-performance inference serving system for large language models (LLMs) and multimodal models (vision, video, audio, diffusion). It provides an OpenAI-compatible API, a Python frontend DSL for programmable inference, and supports a wide range of hardware backends (NVIDIA CUDA, AMD ROCm, Intel XPU, Ascend NPU, Apple MLX). The architecture is a distributed serving runtime (SRT) with a scheduler, model executor, custom CUDA/Triton kernels, and advanced features like speculative decoding (EAGLE, MTP, NGRAM), disaggregated prefill/decode, hierarchical KV cache (HiCache), and quantization (FP8, NVFP4, AWQ, GPTQ). It also includes a Rust-based model gateway for routing and a multimodal generation pipeline for diffusion models. The system is designed for production-scale deployment, powering trillions of tokens daily across hundreds of thousands of GPUs.