Sr Founding Backend Engineer in San Francisco, California at Syndesus

Senior Backend Engineer | Voice AI StartupAbout the CompanyOur 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 RoleAs 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