vLLM
The throughput king. OpenAI-compatible, Apache-2.0, built for serious serving.
vLLM is a high-throughput inference engine born out of UC Berkeley, built around PagedAttention — a memory-management technique borrowed from operating-system paging that lets it batch far more concurrent requests onto the same GPU than naive serving does. It exposes an OpenAI-compatible server, so most existing client code works by changing a base URL. It is the default choice for teams serving one model to real traffic, and the engine underneath a large share of the inference providers you would otherwise pay.
Strengths
- +Highest throughput per GPU of the mainstream engines
- +OpenAI-compatible API — client code often needs no change
- +Apache-2.0 with no feature gates or usage limits
- +Continuous batching keeps the GPU busy under mixed load
Trade-offs
- −You own the GPU, the drivers and the on-call rota
- −No scale-to-zero — an idle GPU still costs whatever it costs
- −Setup assumes comfort with CUDA and Python environments