Senior AI Engineer - Ruby Labs

About Us

Ruby Labs creates and operates innovative consumer products across the health, education, and entertainment industries. Our innovative teams are driving the future of consumer-led products.

About the Role

We are looking for a Senior AI Engineer to own and scale the AI layer of one of our core D2C subscription products. You will be fully responsible for production LLM features and the browser automation built around them end to end — prompt systems, structured outputs, evaluation, observability, and model selection — from first experiment to live release, with quality, reliability, and cost as your accountability.

This is a high-impact role suited for someone who decides with data, not intuition. You work in a modern TypeScript stack: Next.js, Cloudflare Workers and Containers with Hono, Hatchet task queues, Drizzle on Supabase Postgres, and Vercel Blob. Browser automation on Browserbase and Playwright is roughly half of the job.

Key Responsibilities

Prompt Systems & Structured Outputs

• Design dynamic prompt templates with conditional logic and context injection that maximize generation quality.
• Enforce predictable outputs with JSON mode, function calling, Zod/JSON schemas, validators, and repair loops.
• Own complex LLM workflows (LangChain, LlamaIndex, or custom) that integrate cleanly into application logic.

Browser Automation

• Build and maintain browser automation on Browserbase Functions and Playwright that traverses web flows reliably.
• Classify screens with a model inside each traversal, and decide what the model handles versus deterministic code.
• Ship automations as frozen, published workers — versioned, reproducible, and safe to roll back.
• Orchestrate runs through Hatchet with retries, timeouts, and failure traces that explain every broken run.

Evaluation & Experimentation

• Build evaluation pipelines — test datasets, LLM-as-a-judge, RAGAS-style metrics — and score responses and screen classifications in Langfuse.
• Trace complex LLM chains to find bottlenecks in cost, latency, and context-window usage.
• Run A/B experiments across models and prompts through an AI gateway (OpenRouter, Cloudflare AI Gateway); release only on quantitative benchmarks.
• Re-evaluate models as new architectures emerge; fine-tune when domain requirements demand it.

Production Ownership

• Take AI features from experiment to live production on Cloudflare Workers and Containers, and stay accountable after release.
• Manage rate limits, fallbacks, and model cost so features stay reliable at scale.
• Resolve production incidents in owned AI and automation systems with documented root-cause analysis.

Qualifications

• 5+ years of software engineering experience with Node.js, TypeScript, Next.js, and Postgres, including edge or serverless runtimes such as Cloudflare Workers.
• Production browser automation with Playwright (Browserbase or similar): resilient selectors, retries, and failure handling at scale.
• Production experience with dynamic prompting and context injection.
• Structured outputs in production: JSON mode, function calling, Zod/JSON schemas.
• Experience with unified LLM APIs or AI gateways (OpenRouter, Cloudflare AI Gateway) for rate limits, fallbacks, and cost-effective model selection.
• LLM observability with Langfuse or similar tools (tracing, test datasets, scoring integration).
• Evaluation methodology expertise: RAGAS or custom LLM-as-a-judge systems.

Benefits

• Remote Work Environment: Freedom to work remotely from anywhere within ±4 hours of CET.
• Unlimited PTO: Take time off to recharge without counting days, plus paid national holidays.
• Company-provided MacBook: Apple MacBook provided for your day-to-day productivity.
• Flexible Independent Contractor Agreement: Autonomy, tax benefits, and entrepreneurship opportunities.

Interview Process

• Recruiter Screening (40 minutes)
• Technical Interview (60 minutes)
• Final Interview (30 minutes)