I was wondering if it uses something like vLLM[0] or Llama.cpp[1].

Seems to be Llama.cpp via 'Nitro', which was discussed here before [2].

[0] https://github.com/vllm-project/vllm

[1] https://github.com/ggerganov/llama.cpp

[2] https://news.ycombinator.com/item?id=38887531