# AI Product Focus - Senior Full Stack / Rails Engineer (Boston)

**Company:** [Yuma AI](https://hotfix.jobs/companies/yuma-ai)
**Location:** Boston, MA
**Role:** Fullstack Engineering
**Experience:** 5+ years
**Skills:** Ruby on Rails, Postgres, Redis, Sidekiq, Next.js, React, LLMs, A/B Testing, Kubernetes, GCP
**Posted:** 2025-12-04

> Senior full stack engineer focusing on scaling Rails backend, integrating LLMs for AI agents in customer support, and contributing to product iterations with frontend when needed. Requires 5+ years Rails expertise and hands-on AI experience.

## Job Description

## Responsibilities

### Backend Engineering
- Architect, build, and scale large Ruby on Rails applications
- Own major systems within our Rails API, including performance, reliability, and maintainability
- Manage PostgreSQL at scale: schema design, indexing, performance diagnostics
- Maintain and optimize Redis + Sidekiq pipelines for high-throughput workloads
- Lead backend-heavy feature projects, from design to deployment

### AI / LLM Systems
- Integrate, evaluate, and iterate on LLM providers and models
- Design systems that manage non-deterministic model outputs safely and predictably
- Build and own A/B tests, eval pipelines, and agentic workflows
- Optimize for latency, reliability, and cost across LLM-heavy features
- Contribute directly to prompts, agents, and AI system architecture

### Product & Full-Stack Contribution
- Collaborate tightly with founders and engineers to define product requirements
- Jump into frontend (Next.js/React) when needed to ship features end-to-end
- Run rapid product iterations: fast feedback loops, experimentation, data-driven decisions
- Maintain a high bar for product quality while optimizing for speed of execution

## Requirements
- 5–10+ years of experience building and scaling production Rails applications
- Expert-level Ruby on Rails knowledge: ship quickly and safely
- Pragmatic: make thoughtful trade-offs that maximize user value and iteration speed
- Take ownership and thrive in high-velocity environments
- Recent, hands-on experience with LLMs and use AI in day-to-day workflow
- Comfortable navigating ambiguity, experimenting, and working with non-deterministic systems
- Able to contribute across the stack (backend-first, but not backend-only)
- Deeply care about product quality, speed, and delivering great user experience

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**Apply:** https://hotfix.jobs/jobs/2da4fb34-4235-4898-b8c5-1dcf15befaf8
**Canonical:** https://hotfix.jobs/jobs/2da4fb34-4235-4898-b8c5-1dcf15befaf8