Role OverviewAt FlexAI, we're building a high-performance, cloud-agnostic AI compute platform designed for next-generation training and inference workloads. As a
Staff AI Runtime Engineer, you'll play a pivotal role in the design, development, and optimization of the core runtime infrastructure that powers distributed training and deployment of large AI models (LLMs and beyond).
This is a hands-on leadership role - perfect for a systems-minded software engineer who thrives at the intersection of AI workloads, runtimes, and performance-critical infrastructure. You'll own critical components of our PyTorch-based stack, lead technical direction, and collaborate across engineering, research, and product to push the boundaries of elastic, fault-tolerant, high-performance model execution.
What You'll DoLead Runtime Design & Development:- Own the core runtime architecture supporting AI training and inference at scale.
- Design resilient and elastic runtime features (e.g. dynamic node scaling, job recovery) within our custom PyTorch stack.
- Optimize distributed training reliability, orchestration, and job-level fault tolerance.
Drive Performance at Scale:- Profile and enhance low-level system performance across training and inference pipelines.
- Improve packaging, deployment, and integration of customer models in production environments.
- Ensure consistent throughput, latency, and reliability metrics across multi-node, multi-GPU setups.
Build Internal Tooling & Frameworks:- Design and maintain libraries and services that support model lifecycle: training, checkpointing, fault recovery, packaging, and deployment.
- Implement observability hooks, diagnostics, and resilience mechanisms for deep learning workloads.
- Champion best practices in CI/CD, testing, and software quality across the AI Runtime stack.
Collaborate & Mentor:- Work cross-functionally with Research, Infrastructure, and Product teams to align runtime development with customer and platform needs.
- Guide technical discussions, mentor junior engineers, and help scale the AI Runtime team's capabilities.
What You'll Need to Be Successful- 8+ years of experience in systems/software engineering, with deep exposure to AI runtime, distributed systems, or compiler/runtime interaction.
- Experience in delivering PaaS services.
- Proven experience optimizing and scaling deep learning runtimes (e.g. PyTorch, TensorFlow, JAX) for large-scale training and/or inference.
- Strong programming skills in Python and C++ (Go or Rust is a plus).
- Familiarity with distributed training frameworks, low-level performance tuning, and resource orchestration.
- Experience working with multi-GPU, multi-node, or cloud-native AI workloads.
- Solid understanding of containerized workloads, job scheduling, and failure recovery in production environments.
Nice to Have- Contributions to PyTorch internals or open-source DL infrastructure projects.
- Familiarity with LLM training pipelines, checkpointing, or elastic training orchestration.
- Experience with Kubernetes, Ray, TorchElastic, or custom AI job orchestrators.
- Background in systems research, compilers, or runtime architecture for HPC or ML.
- Start up previous experience
This position is In-Person and located at our Santa Clara, CA Office.
What We Offer- A competitive salary and benefits package
- Work on cutting-edge AI infrastructure
- Build products used by developers and enterprises
- High ownership, fast execution, real impact
- Collaborative, high-caliber team
The pay range for this role is:
180,000 - 225,000 USD per year (US)
