Senior Founding Full Stack Engineer

Sarsfield Group; Redwood City (CA); On-site; USD 180,000 - 260,000; Full time

Benefits offered by this job

Unlimited meals and snacks

Gym and commute reimbursement

Job summary

Our client, a fast-growing YC-backed Voice AI startup, is seeking a Founding Senior Full-Stack Engineer in Redwood City, CA. You’ll build the core platform powering millions of AI-driven conversations using React, TypeScript, and Node.js.

You’ll own features end-to-end, from architecture to production deployment, integrate telephony, dashboards, and analytics, and support onboarding. Equity 0.25–0.45% with unlimited meals, gym, and commute reimbursement; full-time on-site role.

Qualifications

• 2+ years of full-stack experience with React, TypeScript, Node.js, or Python.
• CS/CE degree or equivalent practical experience.
• Ownership mindset with the ability to solve problems independently.
• Thrives in fast-paced, dynamic environments.
• Strong communication and collaboration skills.

Responsibilities

• Develop core features including prompt orchestration, dashboards, analytics, and telephony integrations.
• Build full-stack systems from polished UIs to robust APIs and DevOps workflows.
• Own projects end-to-end from architecture to production deployment.
• Support customer onboarding and translate feedback into product improvements.

Skills

React

TypeScript

Node.js

Python

Education

CS/CE degree or equivalent practical experience

Job description

Our client is a fast-growing Y Combinator-backed Voice AI startup transforming sales, support, and customer engagement. With $5M in seed funding and approaching $30M ARR already, achieved with just 20 people, they’re building the standard for voice automation at scale.

The Role

As a Founding Senior Full-Stack Engineer, you’ll build the core platform powering millions of AI-driven conversations. Working with React, TypeScript, and Node.js, you’ll create scalable systems and intuitive interfaces that enable seamless customer experiences.

Key Responsibilities

• Develop core features including prompt orchestration, dashboards, analytics, and telephony integrations
• Build full-stack systems from polished UIs to robust APIs and DevOps workflows
• Own projects end-to-end from architecture to production deployment
• Support customer onboarding and translate feedback into product improvements

Requirements

• 2+ years full-stack experience with React, TypeScript, Node.js, or Python
• CS/CE degree or equivalent practical experience
• Ownership mindset with ability to solve problems independently
• Thrives in fast-paced, dynamic environments
• Strong communication and collaboration skills

Equity: 0.25% - 0.45%

Schedule: Full-time

Location: Redwood City, CA

• Unlimited meals and snacks
• Gym and commute reimbursement

Interview Process

• Online coding assessment (25-30 min)
• Technical phone interviews (2 rounds)
• Onsite/virtual interviews: practical coding, system design, and automation