Senior Software Engineer, Backend
ABOUT RETELL AI
Retell AI is using the first principles to reimagine the call center with cutting edge voice AI.
Since launching 18 months ago, thousands of companies now utilize Retell’s AI voice agents to handle sales, support, and logistics calls that once required large teams of human agents. Backed by Y Combinator, Alt Capital, and other leading investors, we have scaled to $36M ARR with a team of 20 people, up from $5M at the start of 2025.
In 2026, We are expanding our vision to build a CX platform of the AI era where the entire contact center is reimagined as a team of AI employees. We are moving beyond mechanical automation that relies on human finetuning to instead transform core functions into intelligent, opinionated AI roles. Frontline agents, QA analysts, and managers now operate as distinct digital workers that serve as the new interface for customer experience. They execute, monitor, and improve continuously to create a system where software behaves like an organization.
We’re scaling fast, and we’re looking for bold, ambitious people to help us build the gold standard for voice automation. If you want to work on deeply technical challenges, move fast, and make an outsized impact at one of the fastest-growing Voice AI startups in the world, you’ll love it here.
Let’s build the future together.
We’re a top 50 AI app in a16z list: https://tinyurl.com/5853dt2x
#4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025
We're also one of the top ranking startups on: https://leanaileaderboard.com/
ABOUT THE ROLE
As a Senior Backend Engineer, you’ll shape the core systems powering millions of AI-driven conversations. You’ll tackle real-time audio, global telephony, and developer tooling, working across the stack with the founding team. This high-impact role offers rapid feedback loops, customer collaboration, and the chance to define a category-leading product.
KEY RESPONSIBILITIES
Build foundational architecture for Retell's platform, such as prompt orchestration, testing frameworks, observability dashboards, and telephony integrations.
Design scalable backend systems and DevOps workflows for reliable performance across millions of calls.
Lead complex projects from architecture to production, driving delivery and monitoring.
Collaborate with product and design teams to create intuitive APIs and interfaces for quick customer onboarding.
Support customer onboarding, troubleshoot issues, and turn feedback into product improvements.
YOU MIGHT THRIVE IF
Have 2+ years of backend development experience and a strong foundation in CS fundamentals (CS/CE/EE degree or equivalent).
Have worked on scalable, high-performance backend systems — especially anything involving concurrency, data, storage, or distributed components.
Take ownership like a founder and enjoy building core systems that need to be fast, reliable, and correct.
Thrive in fast-moving, ambiguous environments where you learn quickly and solve new technical problems.
Communicate clearly, collaborate well across teams, and move work forward with momentum.
Have startup experience or the grit to operate in a high-velocity environment — bonus points if you’ve worked on infrastructure, databases, or large-scale backend systems.
JOB DETAILS
Cash: 215k - 290k
Equity: Offer Equity
Location: Redwood City, CA, US
US Visas: Retell AI is open to sponsoring work authorization for qualified candidates, including H-1B, TN, L-1, E-3, F-1 (OPT/CPT), and O-1 visas.
OTHER BENEFITS
100% coverage for medical, dental, and vision insurance
$70/day DoorDash credit for unlimited breakfast, lunch, dinner, and snacks
$200/month wellness reimbursement (gym, fitness classes, etc.)
$300/month commuter reimbursement (gas, Caltrain, etc.)
$75/month phone bill reimbursement
$50/month internet reimbursement
COMPENSATION PHILOSOPHY
Best Offer Upfront: Choose from three cash-equity balance options; no negotiation needed.
Top 1% Talent: Above-market pay (top 5 percentile) to attract exceptional builders.
High Ownership: Small teams, >$1M revenue/employee, and significant equity.
Performance-Based: Offers tied to interview performance, not experience or past salaries.
INTERVIEW PROCESS
Online Assessment: Coding questions on practical problem-solving (7 days to complete).
Intro Call (15-20min): Connect with our Founding Recruiter to get a deeper look at the team and the work you'd be doing.
Technical Interview (45 min): Practical coding session focused on code fluency and system design (For frontend roles, we will focus on React-specific questions. For backend roles, we take a technology-agnostic approach.)
Technical Interview (45 min): A system design-focused interview assesses your knowledge of building product-ready systems.
Onsite/Virtual Interviews (2–3 hrs): Hosted in our office if located in the Bay Area or virtual, with three rounds:
Practical Coding: Tackle real-world coding tasks with debugging.
System Design: Architect a production-ready system.
Tools & Automation: Build automations or improve workflows in any basic environment setup like python, java, node.js, etc.
Learn More
Retell AI - API That Turns Your LLM Into A Human-Like Voice Agent
Retell AI Basics: Everything You Need to Start Building Voice Agents
Join Retell AI to build the future of voice automation, shipping impactful code and defining a new standard for AI-driven communication.