Senior Full-Stack Engineer
Join a YC-backed Voice AI startup that scaled from $5M to $36M ARR in under a year with a team of 24 engineers. Profitable, fast-moving, and category-defining — this is a rare chance to own major features end-to-end at an inflection point.
Voice AI at the Inflection Point
This is a fast-growing, YC-backed Voice AI startup that has scaled from $5M to $36M ARR in under a year with a lean team of 24 engineers. The company is profitable, growing organically, and is not dependent on raising its next funding round — giving the engineering team full autonomy to build without the pressure of investor timelines.
Recognized as a top 50 AI app and among the fastest-growing software companies in 2025, the company is on a mission to reimagine the modern contact center using cutting-edge voice AI — turning frontline agents, QA analysts, and managers into intelligent, autonomous AI roles.
The client organization is confidential. All conversations are handled with full discretion. Apply or reach out directly — even if you're not actively looking.
Own It End to End
This is a rare opportunity to join a sub-50-person engineering team building a category-defining AI product. As a Senior Full-Stack Engineer, you will own major features end-to-end — from backend architecture (prompt orchestration, telephony integrations, distributed systems) to polished frontend experiences (dashboards, analytics, customer-facing UIs). You will work directly with the founders and have a meaningful voice in shaping product and engineering culture.
Hiring 6 total: 3 Full-Stack Engineers + 3 Frontend Engineers.
What You'll Build
- Core platform features: prompt orchestration, analytics dashboards, and telephony integrations
- Scalable full-stack systems — from polished UIs to robust APIs and DevOps pipelines
- Customer-facing interfaces that enable fast onboarding (hours, not days)
- Backend distributed systems that handle millions of AI-driven conversations
- Rapid product improvements driven directly by customer feedback
Technical Domain
Who You Are
- 5+ years of full-stack engineering experience, ideally balanced between front-end and back-end
- CS, CE, or EE degree — or equivalent, demonstrable technical foundation
- Sharp, proven React and TypeScript skills with customer-facing UI/UX delivery
- Solid backend experience in Node.js and/or Python
- Deep knowledge of distributed systems and scalable architecture
- Startup DNA: founder-level ownership, comfortable with ambiguity, zero-to-one builder
- Long-term tenure or meaningful impact at a startup or big tech — no serial job-hoppers
- Highly collaborative: raises ideas, questions assumptions, pushes for the best outcome
- Must work on-site in Redwood City, CA five days per week
- Experience at YC startups or as a founding engineer / ex-founder
- Background in Voice AI, NLP, or telephony systems
- AWS infrastructure experience
- Staff or senior-level background at a high-growth company
Candidates who match any of the following will not be considered, regardless of other qualifications.
- No CS/CE/EE degree or equivalent technical depth
- Multiple job stints under 1 year / pattern of frequent moves
- Shallow or unproven React/TypeScript front-end skills
- No real startup or zero-to-one experience
- Cannot or will not work on-site in Redwood City 5 days per week
Comp & Benefits
- $215,000 – $290,000 base (leveled L4–L6 based on interview performance)
- Extremely competitive equity for stage and trajectory
- Full health, dental, and vision insurance
- $70/day DoorDash meal credit
- $300/month commuter benefits
- Cell phone, internet, gym, and wellness allowances
- Location: Redwood City, CA — in-person 5 days/week, flexible hours
- Commitment: 50–70 hours/week — high-intensity startup environment
- Visa: H1B transfers and TN visas supported; expedited H1B available for North America-based candidates
Interview Process
AIONIA Intro Call
Background, fit, and logistics — confidential, no commitment required
Technical Coding Assessment
High-bar SWE-style coding screen
System Design Interview
Architecture and distributed systems deep-dive
On-site Loop
Full interview loop with founders and engineering team