Senior Full Stack Engineer

Rational Dynamics•Berkeley, CA

About The Position

Rational Dynamics builds customized AI reasoning systems for tasks of high cognitive complexity. Our initial market is the world’s leading institutional asset owners. We work very closely with these customers to create specialized, rigorous benchmark datasets encompassing their most valuable and difficult knowledge work. Then we use the benchmarks to construct agentic large reasoning models, applying the same rigor to prove that the models correctly do the work. Customers access the models through a tailored application service, making their most skilled, expensive workers dramatically more productive. We are an early-stage startup. Our founders previously started Voleon, now one of the world’s largest systematic investment managers, and recognized as a longstanding industry leader in applied machine learning. They bring to Rational Dynamics the same research discipline and data-driven focus that succeeded in the unforgiving, high-stakes setting of financial markets. We are looking for entrepreneurial researchers and engineers who want to work on cutting edge agentic AI methods and build out a best-in-class core technical infrastructure. Our work environment is highly collaborative. Your colleagues will be accomplished experts in AI/ML, statistics, and systems engineering.

Requirements

Orientation toward customer impact. You measure your work by whether it solves real problems, not by technical sophistication alone
5+ years of experience building and maintaining full stack applications in production
Track record of shipping full stack applications where reliability and correctness were non-negotiable, not demo-quality or research-only work
Command of modern frontend frameworks (React preferred) and backend development such as PyTorch or JAX
Strong skills in latency and cost optimization at scale, including efficient inference, serving optimization, and resource-aware model deployment
Strong programming skills in a backend language such as Python or Node, along with strong frontend development skills
Comfort operating on a small team with minimal process, high ownership, and significant ambiguity
Demonstrated experience deploying full stack applications in real production environments serving end users or customers

Nice To Haves

Experience with LLM APIs or AI-powered product features such as LangChain or LlamaIndex
Prior work with third-party model APIs such as OpenAI or Anthropic at scale
Experience building or deploying AI-enabled product features integrated into customer-facing applications
Experience in regulated or high-consequence industries such as finance, healthcare, defense, or critical infrastructure
Prior early-stage or small-team experience where you owned architectural and technical decisions end-to-end

Responsibilities

Own, extend, and improve production full stack systems (frontend interfaces, APIs, and backend services): training pipelines, evaluation frameworks, model serving infrastructure, and monitoring. Focus on delivering reliable capability to customers
Optimize application performance, reliability, and user experience with a bias toward correctness in environments where errors are not recoverable
Translate product requirements into production-grade application features that solves real customer problems, as an embedded member of the research & ML team
Design and maintain testing, observability, and monitoring infrastructure across the stack to enable fast, high quality research and deployment to enable Rational Dynamics to move quickly, and deliver a high quality product with confidence
Integrate third-party model APIs and LLM orchestration frameworks into the platform
Support deployment of full stack features in complex enterprise environments
Continuously improve system performance through disciplined benchmarking and iteration