You will own the core infrastructure powering real-time voice AI agents that sound indistinguishable from humans. Managing sub-400ms response times at massive scale, you'll design and operate the backend systems handling millions of concurrent conversations. This is a high-ownership role working directly with PhD founders to transform global telecommunications.
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Senior Backend Engineer at Phonely
We're creating AI agents that handle millions of calls with sub-400ms latency, sounding so natural that callers can't tell the difference 90% of the time. As a Senior Backend Engineer, you'll own the core infrastructure of a system growing 22% week-over-week, working alongside PhD founders to scale toward 1 billion annual calls. If you're a Python and Rust expert who thrives in high-stakes, real-time engineering environments in San Francisco, this is your chance to define a new category of enterprise AI.
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Location
San Francisco, United States
Compensation
$180k-$220k + Equity
Company
Phonely
Role overview
Software
Phonely is a provider of AI-powered voice AI receptionists and fully automated conversational phone solutions that answer calls, schedule appointments, provide customer support, integrate with calendars and CRMs, offer AI analytics, call summaries, and real-time task execution like booking appointments and updating records. It supports natural human-like conversations in multiple languages, voice cloning, and aims to answer 1 billion calls by 2027 for businesses from small to governments.[1][4][7][9]
What you will do
- Architect and scale performance-critical backend services using Python (asyncio/FastAPI) and Rust to maintain sub-400ms latency.
- Build and manage the infrastructure required to handle high-concurrency voice traffic and real-time WebSockets across global enterprise customers.
- Collaborate directly with AI research founders to integrate state-of-the-art voice models into a reliable, production-grade distributed system.
Who this is a fit for
- 5+ years of experience building production backend systems, with a proven track record at later-stage (Series B-D) startups during high-growth phases.
- Expert-level proficiency in Python (FastAPI/asyncio) with professional experience or a strong desire to work in Rust for performance-critical paths.
- Deep technical background in real-time systems, including streaming data, telephony protocols, WebSockets, and low-latency processing in AWS/Kubernetes environments.
Why this role is remarkable
- Ship code that processes millions of calls monthly for thousands of businesses, experiencing 22% week-over-week growth on a path to 1 billion annual calls.
- Work at the bleeding edge of latency engineering, optimizing real-time streaming and telephony systems where every millisecond directly impacts human-like AI performance.
- Join an elite 8-10 person engineering team in SF immediately following a $16M Series A led by Base10 Partners, offering massive equity upside.
How Jack & Jill work together
I get to know what you’re great at, then find roles you’d never find yourself.Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
I recruit from Jack’s network and make the intro when I spot a great match.And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.
Jack gets to know what you're great at and what you want next, then searches 15 million jobs daily and helps you discover roles at companies like this.
Meet Jack
What happens next?
Jack’s an AI agent for job searching and career coaching. He works for you.
Jill is the AI recruiter working for the company. She recruits from Jack’s network.
If your profile’s a match and Phonely wants to meet, Jill will make the intro. In the meantime, Jack will send you excellent alternatives.