Fullstack Engineer (Front-End Spike)

TL;DR

Fullstack Engineer (Front-End Spike) (AI): Building infrastructure for RL training data and evals for frontier AI agents with an accent on high-quality, intuitive user interfaces and end-to-end product features. Focus on translating customer feedback into polished product improvements and optimizing applications for performance and responsiveness.

Location: On-site in the San Francisco Bay Area. Visa sponsorship and relocation support provided for strong candidates to the US.

Company

Infrastructure provider for RL training data and evals for frontier AI agents, backed by YC W25.

What you will do

• Build and ship end-to-end product features across the frontend and backend with a strong emphasis on user experience.
• Translate product and design requirements into high-quality, intuitive user interfaces.
• Optimize applications for performance, responsiveness, and cross-browser compatibility.
• Develop and maintain backend services and APIs that power core product functionality.
• Engage directly with customers to transform real-world feedback into product improvements.

Requirements

• Strong experience owning products end-to-end across the full stack.
• Evidence of rapid learning and technical adaptability (e.g., programming competitions).
• Portfolio of shipped products, side projects, or live demos demonstrating frontend craftsmanship.
• Startup experience in early-stage technology companies.
• Familiarity with current AI tools and LLM capabilities.
• Strong communication skills for remote collaboration across time zones.

Nice to have

• Exceptional portfolio showcasing UI/UX work, interaction design, or creative engineering.
• Experience with reinforcement learning, post-training, or model training workflows.
• Familiarity with product analytics tools and experimentation (e.g., A/B testing).

Culture & Benefits

• 100% covered top-of-the-line medical, dental, and vision insurance via Blue Shield of CA.
• Complimentary lunch and dinner provided in the office.
• Company-wide holiday break from Christmas Eve to New Year’s Day.
• Perks including an Equinox membership, 401k, and commuter benefits.
• Unlimited access to tokens for ChatGPT, Claude Code, Cursor, and other AI tools.

Hiring process

• Two technical interviews.
• One-week work trial.