Senior Full Stack Engineer

As a Senior Full Stack Engineer, you will be one of the first engineers on a small, senior team building AI systems for high-consequence environments. In our customer environments, model failures have real operational impact. Reporting to the Director of Software Engineering, you will join a small, fast-moving team that already has systems in flight. Your job is to find the highest-impact places to contribute to drive forward technical vision, research ideation, and results for customers. You will work directly with research & ML colleagues to translate experiments into deployable capability and ensure that what we ship meets the reliability bar our customers require. This role is a means to make a difference: your judgment about where to focus and your ability to deliver will shape whether Rational Dynamics can build high cognitive complexity systems that enterprises trust with their most critical workflows. We are building a team of people motivated by the future of speed and productivity that will be unlocked that agentic AI will unlock high complexity domains., * 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 confidenceIntegrate 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

• 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

Preferred qualifications

• 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

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.