About
An applied inference optimization lab
RiftStack works on the software layer between models and hardware. We build Emmy, a compiler that generates fast kernels, and a serving stack that runs them efficiently — so the same model costs less and responds faster on the GPUs teams already have.
Team
Track record
A small team building low-level systems for performance-critical software, with backgrounds at Apple, Roblox, and Ubisoft.
50–60% over cuBLAS
FP32 SGEMM in batched mode on the RTX 5090. In non-batched mode cuBLAS still wins.
1,157 tok/s
Qwen3 Coder on a single consumer-class RTX 5090.
ML compiler from scratch
Emmy — tracing, fusion, scheduling, and CUDA codegen in Python.
Join us
Work with us
RiftStack is operated by CloudRift, and open roles are posted there.
See open roles at CloudRiftWe give priority consideration to people who have taken part in a RiftStack hackathon, because we have already seen how they work. Taking part does not guarantee an interview or an offer.