Senior Full-Stack AI Engineer (Rails & React) - Remote

Circle; Poland; Remote; PLN 335,000 - 521,000; Full time

Benefits offered by this job

35 days paid time off

Remote-first / offsite retreats

Job summary

Circle is seeking a strong full-stack engineer for the AI Core team to build AI-powered applications with Rails backend and React frontend. You will ship end-to-end AI projects, design experiments, and help scale AI infrastructure.

We value hands-on AI feature work, rapid experimentation, and collaboration with leaders and designers. This remote role offers global, equity-based compensation and generous PTO, with offsites twice a year.

Qualifications

• 6+ years experience working as a full-stack engineer on high-traffic production applications.
• Strong proficiency in Ruby on Rails, MySQL / PostgreSQL, ReactJS.
• Hands-on experience building AI features in production — shipped at least one real AI use case.
• Strong experimentation mindset — design and run A/B tests, measure results, and iterate quickly.
• Desire to work in a fast-paced environment with autonomy and collaboration.
• Comfortable with ambiguity and learning new technologies quickly.
• Alignment with Circle's values (see career page).
• Proficient in English (CEFR C2 / ILR 5).

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 (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

Ruby on Rails

MySQL / PostgreSQL

ReactJS

AI features in production

Experimentation mindset

Tools

Rails tooling

Job description

Circle is seeking a strong full-stack engineer for the AI Core team to build AI-powered applications with Rails backend and React frontend. You will ship end-to-end AI projects, design experiments, and help scale AI infrastructure.

We value hands-on AI feature work, rapid experimentation, and collaboration with leaders and designers. This remote role offers global, equity-based compensation and generous PTO, with offsites twice a year.