Founding Engineer

Founding Engineer

River · Full-time · New York, USA · 5+ years · US$140K & ~0.25%+

About River

River builds AI voice agents for B2B SaaS sales teams. Our agent talks with prospects in real time: it qualifies them, answers the hard questions, demos the product by actually using it in a browser while it speaks, and follows up until the deal closes. A full AI seller, available 24/7.

We just closed a $2M pre-seed, backed by the founders of companies like Ramp, Kalshi, and JumpCloud.

About the role

Every River conversation runs on a sub-second loop: speech, a rendered avatar, several LLMs, and an agent using a real browser, all live in front of our customers' buyers. Your job is to make that loop fast and rock-solid. Backend and infrastructure are your priority, but you’ll build across the whole product with us.

This is a founding role: you’re a core member of the team, shaping what River becomes, not just keeping it running.

What you'll do

• Own the live-call pipeline: real-time voice, avatar, and browser streaming in one sub-second loop
• Own the infrastructure behind it: deploys, scaling, observability, cost
• Push our browser-use agent forward. River demos real products by controlling a browser live, clicking and navigating complex apps while it talks, and making that reliable is one of the most interesting problems here
• Put the engineering foundations in place as the team grows: monitoring, incident response, testing, evals
• Ship product features across the stack, and talk to customers

Requirements

• 5+ years building and running production backend systems. You've been the person responsible when things break
• Strong infrastructure skills: deploys, observability, scaling on a major cloud
• Real-time or streaming experience (WebRTC, voice, video, websockets), or comparable low-latency work
• Comfortable in TypeScript and Node (we use Next.js, Postgres, Redis)
• Senior, high-ownership mindset. You're fine with ambiguity and you don't wait for a spec
• Real product opinions. You care about what we build, not just how, and you'll tell us when you think we're wrong

Nice to have

• LiveKit or similar real-time media stacks (WebRTC media servers, Pipecat)
• Voice AI, avatars, or media pipelines
• Browser use / computer use, LLM agents, Playwright or CDP, evals
• Early-stage startup or founder experience

Why River

• A founding role, with meaningful equity and a whole domain that's yours from day one
• You work directly with the founders and shape the product, not just the infrastructure
• Genuinely interesting problems: real-time voice AI and browser-use agents, live in front of real customers
• Try the product yourself at rivergtm.com/start