Senior Software Engineer - Backend

Retell 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We believe voice is still the most natural way humans communicate, yet it has been trapped in outdated call centers for decades.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: https://tinyurl.com/5853dt2x

• We're also one of the top ranking startups on: https://leanaileaderboard.com/

• Build 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.

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.

• 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.

• 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 Type: Full-time, 70 hr/week (50 hr/week onsite with flexible hours + 20 hr/week work from home)

• Cash: 215k - 290k

• Equity: 0.25 - 0.45%

• 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.

• 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

• 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.

1. Online Assessment: Coding questions on practical problem-solving (7 days to complete).

2. Intro Call (15-20min): Connect with our Founding Recruiter to get a deeper look at the team and the work you'd be doing.

3. 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.)

4. Technical Interview (45 min): A deep dive into your backend chops and how you think through systems design.

5. Onsite/Virtual Interviews (2–3 hrs): Hosted in our office if located in the Bay Area or virtual, with three rounds:

   1. Practical Coding: Tackle real-world coding tasks with debugging.

   2. System Design: Architect a production-ready system.

   3. Tools & Automation: Build automations or improve workflows in any basic environment setup like python, java, node.js, etc.

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Join Retell AI to build the future of voice automation, shipping impactful code and defining a new standard for AI-driven communication.