vLLM's core mechanism is PagedAttention, which the docs describe as a paged memory management approach for the KV cache — the part of GPU memory that normally fragments and wastes capacity at scale. Continuous batching sits on top of that, keeping the GPU fed instead of waiting for a fixed batch to fill. The result, per vendor benchmarks at perf.vllm.ai, is significantly higher throughput per GPU than naive serving setups. It exposes an OpenAI-compatible REST API, so existing client code needs no rewrite. The ceiling arrives when you need multi-node tensor parallelism beyond what your hardware topology supports, or when you're serving models on non-NVIDIA silicon — AMD ROCm and CPU paths exist, but community reports suggest NVIDIA CUDA gets the fastest fixes and the deepest optimization.