Senior Software Engineer, Backend

About Retell AIRetell 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.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 can act as frontline agents, QA analysts, and managers — continuously executing, monitoring, and improving customer interactions.We're growing quickly and looking for ambitious builders who want to tackle hard technical problems, move fast, and have real impact at one of the fastest-growing voice AI startups.Let's build the future together.We're a top 50 AI app in a16z list#4 on Brex's Fast-Growing Software Vendors of 2025We're also one of the top ranking startupsAbout 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 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 DetailsCash: 215k - 290kEquity: Offer EquityLocation: 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 ProcessIntro Call (15-20min): Connect with our 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: