Note: The job is a remote job and is open to candidates in USA. Circle is building an AI-powered all-in-one platform for digital businesses. The Senior Full-Stack Software Engineer will develop and ship end-to-end AI solutions using Ruby on Rails and React, including AI agents, retrieval-augmented generation, evaluations, observability, and LLM infrastructure. The role also involves experimentation, performance optimization, and collaboration with leaders and designers to bring AI features into production.
Responsibilities
- Ship full-stack AI projects end-to-end on a product built in Ruby on Rails backend and React frontend
- Design and run experiments (including A/B tests, AI evaluations, or others) to validate AI features, measure impact, and guide iteration
- Build and integrate components for AI infrastructure and optimize them for performance and reliability to support production-level inferencing
- Improve processes, tools, and systems to scale AI features into production-ready solutions
- Help us stay up-to-date with the cutting-edge AI research, techniques, and tools
- Work closely with Circle's leaders and designers throughout the feature design process
- Foster a bias for action by prioritizing speed of iteration, experimentation, and learning, while maintaining high standards of code quality and user experience
Skills
- 6+ years experience working as a full-stack engineer on high-traffic production applications. You've dealt with the challenges that come with scale — query optimization, careful migrations, performance bottlenecks
- Strong proficiency in Ruby on Rails, MySQL / Postgresql, ReactJS . Familiarity with both frontend and backend is necessary, but a high degree of proficiency in both is not a requirement
- Hands-on experience building AI features in production — whether RAG systems, AI agents, or LLM-powered tools. You've shipped at least one real AI use case, not just prototypes
- Strong experimentation mindset — you're comfortable designing and running A/B tests, measuring results, and iterating quickly to discover what works and what doesn't
- A desire to work in an environment which values speed of iteration and individual autonomy, while also embracing personal accountability and the ability to collaborate effectively as part of a dynamic team
- Comfortable in a fast-paced environment with a certain level of ambiguity, especially when learning and picking up new technologies when projects require it
- Strong alignment with our values, find our values on our career page if you haven't read up on them yet
- You are proficient in English (spoken, written, and reading) at a CEFR Level C2 / ILR Level 5
Benefits
- Equity in the company with ongoing refresh grants
- 35 days of paid time off each year
- A remote-only team
- Company retreats twice a year in incredible destinations around the world
- Incredible flexibility and autonomy
- A benefits package that supports health, wellbeing, and professional growth
Company Overview
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