Senior Backend Software Engineer

About Retell AiRetell AI is using the first principles to reimagine the call center with cutting edge voice AI.We believe voice is still the most natural way humans communicate, yet it has been trapped in outdated call centers for decades. Our mission is to bring intelligence, empathy, and speed to every phone conversation between businesses and their customers.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, Altman Capital, and other leading investors, we have scaled to $30M ARR with a team of 20 people, up from $5M at the start of 2025.Now, 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 of voice automation together.We're a top 50 AI app in a16z list: We're also one of the top ranking startups on: CULTUREBuild the Dream Team: We hire high performers who work onsite in the San Francisco Bay Area, move fast, and collaborate deeply. Feedback is open, direct, and constant.Customer obsession. We start with the customer and work backwards. Every job and task matters only if it ultimately benefits the customer.Insist on the Highest Standards: We ship products you're proud to show everyone — even if it means spending more time perfecting them.We like to keep it real, we move fast, build fast, and change fast. That's part of the fun for us, but we know it's not for everyone.About The RoleAs 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 ResponsibilitiesBuild 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 IFHave 2+ years of backend development experience with a degree in CS, CE, or EE.Take ownership like a founder, with a passion for impactful software.Thrive in fast-paced, ambiguous environments, solving new problems with curiosity.Communicate clearly, collaborate across teams, and drive momentum.Have startup experience or grit to adapt, with bonus points for cloud infra/DevOps knowledge.JOB DETAILSJob Type: Full-time, 70 hr/week (50 hr/week onsite with flexible hours + 20 hr/week work from home)Cash: 215k - 290kEquity: %Location: Redwood City, CA, USUS 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 Benefits100% 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 reimbursementCompensation PhilosophyBest 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 PROCESSOnline Assessment (25–30 min): 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 Phone Interview 2 (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.)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, , etc.Learn MoreRetell AI - API That Turns Your LLM Into A Human-Like Voice AgentRetell AI Basics: Everything You Need to Start Building Voice AgentsJoin Retell AI to build the future of voice automation, shipping impactful code and defining a new standard for AI-driven communication.