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

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 youll 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 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 -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.