Senior Software Engineer, Backend

ABOUT RETELL AI Retell AI is using first-principles thinking to reimagine the call center with cutting-edge voice AI. Thousands of companies now use 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've scaled to $80M in ARR with a team of 50, up from $5M at the start of 2025, and are now valued at over $1.5B. Our vision for 2026 is to build a modern CX platform where entire contact centers are powered by AI. Instead of basic automation that needs constant human tuning, we're creating intelligent AI “workers” that act as frontline agents, QA analysts, and managers, continuously executing, monitoring, and improving every customer interaction. We're growing fast and looking for ambitious builders who want to tackle hard technical problems, move quickly, and have a real impact on one of the fastest-growing voice AI companies in the world. Let's build the future together. Recent recognition: - No. 1 Best Places to Work in the Bay Area, San Francisco Business Times 2026 - Top 50 AI Apps, a16z (2025) - 3 Fastest-Growing Software Company, G2 Best Software Awards 2026 - Best Agentic AI Software, G2 Best Software Awards 2026 - 4 Fastest-Growing Software Vendor, Brex Benchmark 2025 - Enterprise Tech 30 Class of 2026, Nasdaq & Wing VC - Top-Ranked Startup, Lean AI Leaderboard - Backed by Y Combinator   ABOUT THE ROLE Retell AI transforms customer experience with voice AI for enterprises, including customers like CVS/Aetna, American Airlines, Lenovo, and Grab. We have more customer stories than we can tell! 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: 200k - 300k - 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 1. Intro Call (15-20min) : Connect with our Recruiter to get a deeper look at the team and the work you'd be doing. 2. 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.) 3. Technical Interview (45 min) : A system design-focused interview assesses your knowledge of building product-ready systems. 4. Onsite/Virtual Interviews (2–3 hrs) : Hosted in our office if located in the Bay Area or virtual, with three rounds: LI-JC1