Senior Full Stack Engineer (Back-End), AI Startup, San Francisco (On-Site)

Jobs in JS; American Fork (UT); On-site; USD 180,000 - 240,000; Full time

Benefits offered by this job

On-site in SF

Job summary

Jobs in JS is hiring an urgent backend-leaning full-stack engineer to work directly with the CTO in San Francisco, building and scaling core infrastructure for a $30M seed-stage AI platform. This is a full-time on-site role five days a week at the Presidio.

You'll ship real-time backend systems, edge compute with Cloudflare Workers, Durable Objects, and a modern stack including TypeScript, Postgres, Docker, and various tooling.

Qualifications

• 5+ years of production backend engineering with on-call experience.
• Proficient in TypeScript; backend-first, full-stack across production stack (TypeScript, Cloudflare Workers, Durable Objects, Hono, Drizzle ORM, Postgres).
• Experience shipping real-time systems (WebSockets, SSE, event streaming) to external users.
• Ability to design distributed systems and justify trade-offs.
• Experience shipping infrastructure used by external users, with clear incident ownership.
• Willing to relocate to San Francisco Bay Area for on-site five days/week.

Responsibilities

• Build and scale core backend infrastructure for a seed-stage AI platform.
• Develop edge compute layers using Cloudflare Workers and durable deployments.
• Implement real-time communication and data streaming at production scale.
• Design distributed systems and create runbooks for incident handling.
• Participate in on-call rotation and own incident resolution end to end.

Skills

Backend engineering

TypeScript

Cloudflare Workers

WebSockets

Durable Objects

Postgres

Docker

System design

On-call experience

Tools

Hono

Drizzle ORM

Vercel AI SDK

SST

React

Vite

Fly.io

Job description

Urgent hire. Backend-leaning full-stack engineer working directly with the CTO to build and scale core infrastructure for a $30M seed-stage AI platform. 5 days a week on-site at the Presidio, San Francisco. Full-time.

What you'll build

• Core backend infrastructure: agent runtimes, SSE streaming pipelines, task queues, and multi-model LLM provider routing, shipped to real external users.
• Edge compute layer using Cloudflare Workers and Durable Objects with Fly.io blue-green and canary deployments.
• Real-time systems at scale: WebSockets, SSE, event streaming, and message queues under production load.
• Distributed system architecture: consistency tradeoffs, failure modes, and operational runbooks for a 15-person team moving fast.
• On-call rotation: you carry a pager, respond to incidents, and own resolution end to end.

Required

• 5+ years of production backend engineering, including on-call. Can name a specific incident, what broke, and how it was resolved.
• TypeScript fluent, backend-primary. Full stack across the production stack: TypeScript, Cloudflare Workers, Durable Objects, Hono, Drizzle ORM, Postgres, Zod, SST, Vercel AI SDK, Docker, React, Vite.
• Has shipped real-time systems to external users in production: WebSockets, SSE, event streaming, or message queues, with specific scaling bottlenecks they can describe.
• Has designed distributed systems and made concrete consistency tradeoffs. Can explain what they chose, what they gave up, and why.
• Has shipped infrastructure that real external users depended on, not internal tooling. Can name the system, the user load, and the operational responsibility they held.
• Has worked with LLM agent loops, model routing layers, or tool-use architectures. Does not need ML depth, but must not be starting from zero on agent interaction patterns.
• Based in San Francisco Bay Area or willing to relocate before the start date for 5-days-a-week on-site work at the Presidio.

Visa and relocation:

• US work authorization required. O-1 or J-1 sponsorship considered for exceptional candidates only. H-1B is not on the table.
• Europeans eligible for O-1 are considered. US-based candidates are prioritized.

Disqualifiers

• No US work authorization and not O-1 or J-1 eligible.
• Unwilling to work on-site 5 days a week in San Francisco. Not negotiable.
• Pure frontend background with no substantial production backend or distributed systems experience.
• No exposure to agent loops or model interaction patterns. The ramp from zero is too large for this hire.
• Built only internal tooling, never shipped infrastructure to external users.
• Needs written specs and fully async communication to function. The office is small, open, and high-energy. Information flows through direct, impromptu conversation.

Strong plus

• Production experience with Cloudflare Workers, Durable Objects, or serverless edge compute.
• Has built agent runtimes, model routing layers, or tool-use architectures with LLMs in production.
• Ex-founder or ex-CTO. Most of the current team are former founders or CTOs. Signals high agency and comfort with ambiguity.
• Early engineer at an AI-native startup. The existing team came almost entirely from small AI-native companies.
• Actively building or experimenting with AI outside of work, not just following the space. Has tried the product before interviewing.
• Open to a paid in-person work trial of a few days up to two weeks. Roughly 70% of trial candidates convert to full-time. Accommodation and flights covered for relocating candidates.