Senior Software Engineer
ArcadiaAbout the role
Senior Software Engineer, Founding Team
San Francisco, CA (onsite)
The Opportunity
A high-growth startup is building the infrastructure to measure how LLMs actually perceive and process data, giving teams visibility into model behavior that's historically been a black box. They're hiring a Senior Software Engineer to join the founding team for a true 0→1 opportunity, architecting the core product alongside a small, technical founding group.
You'll move fluidly across frontend, backend, and applied AI, including building and orchestrating AI agents end to end, with real ownership in a fast-paced, autonomous environment.
The Stack
TypeScript/React on the frontend, Python on the backend. You'll be working directly with LLMs and model outputs, building the evaluation and measurement frameworks from scratch.
What You'll Do
Own full stack architecture decisions from day one, spanning frontend to backend
Design and build systems that evaluate and quantify LLM perception of structured and unstructured data
Build and orchestrate agentic workflows for automated evaluation, data processing, and model behavior analysis
Work directly with LLMs and model outputs to build novel measurement and evaluation frameworks
Ship product end to end, from data pipelines to user-facing interfaces
Set technical standards and engineering culture as one of the first hires
Work directly with founders and have real say in product features, roadmap, and technical decisions
What Makes You a Fit
Strong full stack experience with TypeScript, React, and Python in production environments
Hands-on experience building with or around LLMs, whether that's evals, fine-tuning, RAG, or applied AI product work
Founding engineer, founder, or very early-stage startup experience, comfortable with ambiguity and moving/shipping fast
Genuinely excited to be hands-on at every layer of the stack
Strong communication skills
Why This Role
One of the first engineering hires at a high-growth, well-backed startup tackling a problem that's only getting more critical as LLMs get embedded everywhere. Huge ownership, huge technical surface area, and a real seat at the table for foundational product decisions.
Responsibilities
- Own full stack architecture decisions from day one, spanning frontend to backend
- Design and build systems that evaluate and quantify LLM perception of structured and unstructured data
- Build and orchestrate agentic workflows for automated evaluation, data processing, and model behavior analysis
- Work directly with LLMs and model outputs to build novel measurement and evaluation frameworks
- Ship product end to end, from data pipelines to user-facing interfaces
- Set technical standards and engineering culture as one of the first hires
- Work directly with founders and have real say in product features, roadmap, and technical decisions
Qualifications
- Strong full stack experience with TypeScript, React, and Python in production environments
- Hands-on experience building with or around LLMs, whether that's evals, fine-tuning, RAG, or applied AI product work
- Founding engineer, founder, or very early-stage startup experience, comfortable with ambiguity and moving/shipping fast
- Genuinely excited to be hands-on at every layer of the stack
- Strong communication skills
Skills mentioned
About Arcadia
Arcadia is a high-performance recruitment firm operating on a top percentile trajectory across North America, with growth speed and per-head productivity placing it among the top 1–3% of agencies in the global market place. Built to challenge the traditional model, Arcadia has scaled to a multi-million dollar run rate in under a year through disciplined execution, selective partnerships, and consistent, elite-level performance. The business is designed for precision, output, and scale. Our footprint spans North America from coast-to-coast, with presence in Toronto and New York as well as key U.S. markets including Charlotte, Boston, San Francisco, Atlanta, and Miami. We partner with companies backed by leading venture firms including Y Combinator, Andreessen Horowitz, General Catalyst, Founders Fund, Accel, and GV, delivering talent that directly impacts outcomes at the edge of innovation. At the same time, we work with mid-market and enterprise organizations across North America, enabling access to the same caliber of talent, speed, and precision required to compete in an AI-driven landscape. Arcadia sits in a category that is not widely accessible, nor easily replicated. Built on Trust. Delivered with Discipline. Rooted in Integrity.