Founding Software Engineer

About the Role

We’re an early-stage stealth startup building a new kind of platform for generative media. Our mission is to enable the future of real-time generative applications: we’re building the foundational tools and infrastructure that make entirely new categories of generative experiences and applications finally possible.

We’re a small, focused team of ex-YC and unicorn founders and senior engineers with deep experience across 3D, generative video, developer platforms, and creative tools. We're backed by top-tier investors and top angels, and we're building a new technical foundation purpose-built for the next era of generative media.

We’re operating at the edge of what’s technically possible: high-performance inference and real-time orchestration of multimodal models. As one of our founding engineers, you’ll play a key role in architecting the core platform, shaping system design decisions, and owning critical infrastructure from day one.

If you're excited about architecting and building high-performance infrastructure that empowers the next generation of developers and unlocks entirely new products categories, we’d love to talk.

About the Role

We’re looking for a Founding Engineer, ML Performance & Systems with deep expertise in high-performance ML infrastructure. This is a highly technical, high-impact role focused on squeezing every drop of performance from real-time generative media models.

You’ll work across the model-serving stack, designing novel architectures, optimizing inference performance, and shaping Reactor’s competitive edge in ultra-low-latency, high-throughput environments

What You’ll Do

• Drive our frontier position on real-time model performance for diffusion models
• Design and implement a high-performance in-house inference engine
• Focus on maximizing throughput and minimizing latency and resource usage
• Develop performance monitoring and profiling tools to identify bottlenecks and optimization opportunities

Minimum Qualifications

• Proficiency in building and maintaining full-stack web applications
• Experience with modern frameworks and languages such as Python, Next.js, and Postgres
• Strong understanding of API design principles, authentication strategies (OAuth, API keys), and SDK architecture
• Familiarity with developer tooling and platforms—understanding what makes great documentation, intuitive DX, and reliable SDKs
• Comfort working across the stack—from database models and cloud infrastructure to front-end components and user flows

Additional beneficial experience:

• Experience with OpenAPI / Swagger and API gateway design
• Familiarity with WebSockets, streaming APIs, or real-time collaboration tools
• Exposure to developer community engagement—e.g., writing tutorials, supporting integrations, or maintaining SDKs

• Competitive SF salary and foundational team equity