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.

Requirements

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

Fully remote: work from anywhere in the world!
Autonomy and trust to do your job: we care about outcomes over everything else.
Paid time away: all employees are given 35 days of PTO annually. We also offer a paid sabbatical after 5 years.
Generous U.S. benchmarked compensation and startup equity no matter where you are in the world.*
Awesome medical coverage with 100% coverage for you and your family, or medical reimbursement options where applicable!*
Parental leave for parents expanding their family, or just starting one.
Home office stipend to help you get up and running.
Learning & development stipend to help you level up your professional skills.
Annual bonus potential for roles that don't already receive variable income or commission.
Company retreats: Twice a year, the Circle team gets together for a fully paid company retreat in incredible places around the world! We’ve had past retreats in Colombia, Portugal, and Mexico, with more planned on the horizon.

Applicant Tracking System Keywords

Tip: use these terms in your resume and cover letter to boost ATS matches.

Ruby on RailsReactJSMySQLPostgresqlAI featuresA/B testingperformance optimizationproduction-level inferencingquery optimizationscalable applications

experimentation mindsetcollaborationpersonal accountabilityadaptabilitycommunicationteamworkautonomyproblem-solvingspeed of iterationlearning agility