Sr Founding Backend Engineer

Senior Backend Engineer | Voice AI Startup About the Company Our client is a fast-growing Y Combinator-backed Voice AI startup transforming sales, support, and customer engagement. With $5M in seed funding and approaching $30M ARR already, achieved with just 20 people, they're building the standard for voice automation at scale. The Role As a Founding Senior Backend Engineer, you'll build the core systems powering millions of AI-driven conversations. You'll work on real-time audio, global telephony, and developer tooling, collaborating directly with the founding team to define a category-leading product. Key Responsibilities Build foundational architecture including 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, owning delivery and monitoring Collaborate with product and design teams to create intuitive APIs for rapid customer onboarding Support customer onboarding, troubleshoot issues, and translate feedback into product improvements Requirements 2+ years backend development experience CS, CE, or EE degree or equivalent practical experience Ownership mindset with passion for impactful software Thrives in fast-paced, ambiguous environments with strong problem-solving skills Clear communication and cross-functional collaboration abilities Bonus: Startup experience and cloud infrastructure/DevOps knowledge Compensation & Benefits Salary: $200K - $280K Equity: 0.25% - 0.45% Schedule: Full-time, 70 hrs/week (50 onsite + 20 remote, flexible hours) Location: Redwood City, CA 100% medical, dental, vision coverage Unlimited meals and snacks Gym and commute reimbursement Visa sponsorship available (H1B, TN, L-1, E-3, F-1, O-1) Interview Process Online coding assessment (25-30 min) Technical phone interviews (2 rounds focusing on data structures and algorithms) Onsite/virtual interviews: practical coding, system design, and automation