Senior Full-Stack Software Engineer, AI Core

Circle

Senior full-stack engineer building production AI agents, RAG, and LLM infrastructure for Circle’s online community platform. Shipping Rails and React features through rapid experimentation.

Posted 8/12/2026full-timeRemote • 🇺🇸 United StatesSenior💰 $130,000 - $140,000 per yearWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in full-stack development with a focus on Ruby on Rails and React, alongside hands-on experience in building and deploying AI features in production environments. Proficient in designing experiments and optimizing systems for performance and reliability while maintaining high standards of code quality and user experience.

Highest-signal resume keywords

Full-Stack DevelopmentRuby On RailsReactJSAI Feature DevelopmentA/B Testing

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Applicant Tracking System Keywords

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Hard Skills

Ruby On RailsReactJSMySQLPostgreSQLAI Feature DevelopmentA/B TestingQuery OptimizationPerformance Bottleneck ResolutionProduction Inference OptimizationExperiment Design

Soft Skills

AutonomyPersonal AccountabilityEffective CollaborationAdaptabilityLearning Agility

Industry Keywords

High-Traffic Production ApplicationsAI InfrastructureRAG SystemsAI AgentsLLM-Powered Tools

Tech Stack

Tools & technologies

MySQLPostgresReactRubyRuby on Rails

About the role

Key responsibilities & impact

Ship full-stack AI projects end-to-end on a Ruby on Rails backend and React frontend
Design and run experiments, including A/B tests and AI evaluations, to validate AI features and measure impact
Build and integrate AI infrastructure components and optimize them for performance and reliability in production inference
Improve processes, tools, and systems to scale AI features into production-ready solutions
Stay up-to-date with cutting-edge AI research, techniques, and tools
Work closely with Circle's leaders and designers throughout feature design
Prioritize speed of iteration, experimentation, and learning while maintaining high code-quality and user-experience standards

Requirements

What you’ll need

6+ years of experience as a full-stack engineer on high-traffic production applications
Experience with scale-related challenges, including query optimization, careful migrations, and performance bottlenecks
Strong proficiency in Ruby on Rails, MySQL/PostgreSQL, and ReactJS
Familiarity with both frontend and backend development
Hands-on production experience building AI features such as RAG systems, AI agents, or LLM-powered tools
At least one real AI use case shipped to production, not only prototypes
Ability to design and run A/B tests, measure results, and iterate quickly
Ability to work with autonomy, personal accountability, and effective collaboration
Comfort working in a fast-paced, ambiguous environment and learning new technologies
Strong alignment with Circle's values
English proficiency at CEFR Level C2 / ILR Level 5

Benefits

Comp & perks

$130,000 - $140,000 USD per year
Equity in the company with ongoing refresh grants
35 days of paid time off each year
Twice-yearly company retreats/offsites in destinations around the world
Incredible flexibility and autonomy
Benefits package supporting health, wellbeing, and professional growth