Founding Backend Engineer (Agent Infra) - Developer AI Startup | San Francisco

You've built backends from scratch and you use coding agents every day. Own the infrastructure that runs them at scale.

A seed-stage startup in San Francisco runs real coding sessions in popular AI coding agents so developer-tool companies can see their product through an agent's eyes: does the agent choose it, can it work with it, and where does it struggle or go elsewhere? Well-known developer-tool companies already rely on it. As the third engineer, you'll own the core backend within your first few months.

What you'll own

• The sandboxes, AI gateway and orchestration that run large numbers of coding-agent sessions
• Shipping to customers, gathering feedback and shipping again within days
• Your own technical decisions, defended at a weekly round table where the best idea wins
• Performance and scale as usage grows

Must-haves

• You've created backend systems for production yourself, from a blank page, and can explain each choice (relying on a separate infra team for deployment isn't the same)
• 3+ years of experience, with your latest role as a hands-on engineer at an early-stage, fast-growing startup
• You want to stay an individual contributor
• Comfortable working with coding agents every day
• Working from the San Francisco office five days a week, 9-9-6 (no remote or hybrid)
• Authorised to work in the US without visa sponsorship

Bonus points

• Agent sandboxes, AI gateways or agent infrastructure on AWS and containers
• Postgres, ClickHouse, TypeScript or Python
• Founding engineer more than once, open-source work, side projects with real users or agent hackathons

What's in it for you

• $200k–$250k base + 0.5–1% equity
• Full ownership of the core backend as one of the first engineers
• A team that ships in days, not weeks

Good to know

• Full-time, on-site in San Francisco, 9-9-6
• No visa sponsorship for this role
• Process: first screen → 60-minute technical interview (a walk-through of a system you built and a short system-design exercise) → on-site in San Francisco → offer

When you apply, please include

• Your CV (PDF), your LinkedIn URL, and GitHub if you have one
• A backend you built from nothing: its purpose, how it works and the trade-offs you made
• A scale or performance problem you solved, with numbers
• Your current location, and confirmation that five days a week in San Francisco works for you
• Confirmation that you can work in the US without sponsorship
• Your base salary expectation, your notice period, and any other interview processes you're in

Does this sound like you? Apply now. If you're a match, we'll be in touch within 3 working days.

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