Senior Software Engineer, Infrastructure at Retell AI | San Francisco

Join the Revolution at Retell AIRetell AI is pioneering the future of call centers through innovative voice AI, driven by first principles thinking.In just 18 months since our inception, we have empowered thousands of businesses with our AI voice agents, transforming how sales, support, and logistics calls are managed—previously requiring extensive human teams. Supported by prestigious investors such as Y Combinator and Alt Capital, we've rapidly scaled from $5M ARR to an impressive $36M ARR with a compact yet dynamic team of 20.Our ambition for 2026 is to create a revolutionary customer experience platform, where entire contact centers are powered by AI. Moving beyond basic automation, we aim to develop intelligent AI “workers” that serve as frontline agents, QA analysts, and managers, continuously enhancing customer interactions without the need for constant human oversight.As we expand, we are seeking passionate engineers who are eager to solve challenging technical problems, act swiftly, and make a significant impact in one of the fastest-growing voice AI startups. Let’s shape the future together.

Join Our Innovative Team at Retell AIRetell AI is at the forefront of revolutionizing the call center industry through advanced voice AI technology. In just 18 months since our inception, we have empowered thousands of businesses to optimize their sales, support, and logistics calls, which previously relied on large teams of human agents. Supported by prominent investors including Y Combinator and Alt Capital, we've achieved remarkable growth, scaling from $5 million to $36 million in annual recurring revenue (ARR) while expanding our talented team to 20 members.Our ambitious vision for 2026 is to develop a state-of-the-art customer experience platform, transforming entire contact centers with AI. Unlike traditional automation that requires ongoing human oversight, we are building intelligent AI "workers" capable of functioning as frontline agents, quality assurance analysts, and managers, constantly enhancing customer interactions.If you are a passionate innovator eager to solve complex technical challenges and make a tangible impact at one of the fastest-growing voice AI startups, we invite you to join us in shaping the future.Ranked among the top 50 AI applications by a16z: a16z List4th on Brex's Fast-Growing Software Vendors of 2025: Brex BenchmarkFeatured as a leading startup on: Leanaileaderboard

Join Retell AIAt Retell AI, we leverage first principles to revolutionize the call center experience through innovative voice AI technology.In just 18 months since our launch, our AI voice agents have been adopted by thousands of companies to manage sales, support, and logistics calls, significantly reducing the need for large teams of human agents. Supported by Y Combinator, Alt Capital, and other notable investors, we've achieved impressive growth, scaling from $5M to $36M ARR with a dedicated team of 20.Looking ahead to 2026, we aim to create a comprehensive AI-powered Customer Experience (CX) platform that transforms entire contact centers. Instead of simple automation requiring ongoing human oversight, we are developing intelligent AI "workers" that serve as frontline agents, QA analysts, and managers — perpetually executing, monitoring, and enhancing customer interactions.We're experiencing rapid growth and are on the lookout for passionate innovators eager to tackle complex technical challenges, accelerate progress, and make a significant impact at one of the leading voice AI startups.Let’s build the future together.Ranked in the top 50 AI applications by a16z: https://tinyurl.com/5853dt2x#4 on Brex's Fast-Growing Software Vendors list for 2025: https://www.brex.com/journal/brex-benchmark-december-2025One of the top startups on: https://leanaileaderboard.com/

About Retell AI Retell AI builds voice AI technology for call centers, helping thousands of companies handle sales, support, and logistics calls with AI voice agents. Since launching 18 months ago, the company has grown annual recurring revenue from $5M to $50M, backed by investors including Y Combinator and Alt Capital. Our Mission By 2026, Retell AI aims to deliver a customer experience platform powered entirely by AI. The vision goes beyond basic automation: intelligent agents will take on roles as frontline workers, quality assurance analysts, and managers, improving customer interactions while reducing the need for ongoing human involvement. Recognition Ranked among the top 50 AI applications by a16z (a16z List) #4 on Brex's Fast-Growing Software Vendors of 2025 (Brex Benchmark) High placement on the Leana AI Leaderboard Working at Retell AI The team is expanding quickly and welcomes those who want to solve tough problems and help shape the future of voice AI. Retell AI is based in the San Francisco Bay Area and continues to grow as one of the industry's fastest-moving startups.

Join Retell AI as a Senior Machine Learning EngineerRetell AI is at the forefront of revolutionizing the call center industry using groundbreaking voice AI technology. Within just 18 months of our inception, we have empowered thousands of businesses with our AI voice agents capable of managing sales, support, and logistics calls that traditionally required extensive human teams.Supported by renowned investors, including Y Combinator and Alt Capital, our journey has seen us scale from $5M to an impressive $36M ARR with a dedicated team of 20. Our ambition for 2026 is to develop a state-of-the-art customer experience platform, transforming entire contact centers with AI. We are building intelligent AI “workers” that will serve as frontline agents, quality assurance analysts, and managers—constantly executing, monitoring, and enhancing customer interactions.We are rapidly expanding and seeking passionate innovators eager to solve complex technical challenges and make a tangible impact in one of the fastest-growing voice AI startups. Together, let's shape the future of customer interactions.

About Retell AIAt Retell AI, we are pioneering the future of call centers through innovative voice AI technology. Our cutting-edge solutions are transforming how companies engage with customers.In just 18 months since our inception, we've empowered thousands of businesses with our AI voice agents that efficiently manage sales, support, and logistics calls, significantly reducing the need for large teams of human agents. Supported by industry-leading investors including Y Combinator and Alt Capital, we've grown our annual recurring revenue from $5M to an impressive $36M while expanding our team from 5 to 20 talented individuals since 2025.Our ambitious vision for 2026 is to develop a state-of-the-art customer experience platform where entire contact centers are driven by AI. Unlike basic automation requiring constant human oversight, we’re engineering intelligent AI “workers” capable of serving as frontline agents, quality assurance analysts, and managerial roles, all while optimizing customer interactions continuously.We are rapidly expanding and seeking driven builders who thrive on solving complex technical challenges, act decisively, and wish to make a tangible impact in one of the fastest-growing voice AI startups.Join us in shaping the future!Recognized as a top 50 AI application in the a16z list: https://tinyurl.com/5853dt2xRanked #4 in Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025Featured among the top startups on: https://leanaileaderboard.com/

ABOUT RETELL AIRetell AI is revolutionizing the call center landscape with cutting-edge voice AI technology founded on first principles.In just 18 months since our inception, thousands of companies trust Retell’s AI voice agents to manage sales, support, and logistics calls that traditionally required extensive teams of human agents. Supported by prestigious investors such as Y Combinator and Alt Capital, we have rapidly scaled to $36M ARR with a dedicated team of 20, up from $5M at the start of 2025.Our vision for 2026 is to establish a modern customer experience platform that empowers entire contact centers with AI. Rather than relying on basic automation that requires constant human oversight, we are developing intelligent AI “workers” that serve as frontline agents, quality assurance analysts, and managers — continuously executing, monitoring, and enhancing customer interactions.We are in a phase of rapid growth and are seeking ambitious innovators eager to solve complex technical challenges, move at a fast pace, and make a tangible impact at one of the fastest-growing voice AI startups.Join us in building the future together.Recognized as a top 50 AI application on a16z's list: https://tinyurl.com/5853dt2xRanked #4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025Also listed among the top startups on: https://leanaileaderboard.com/

About Retell AIRetell AI is pioneering the future of customer service by leveraging first principles to transform the call center experience through advanced voice AI technology.In just 18 months since our inception, our innovative AI voice agents have been utilized by thousands of companies to efficiently manage sales, support, and logistics calls, significantly reducing the need for large teams of human agents. With the backing of esteemed investors such as Y Combinator and Alt Capital, we have achieved an impressive $36 million ARR, growing from $5 million at the beginning of 2025 with a dedicated team of 20 professionals.Our ambitious vision for 2026 is to develop a state-of-the-art CX platform powered entirely by AI. We aim to create intelligent AI 'workers' that will function as frontline agents, QA analysts, and managers, capable of autonomously executing, monitoring, and enhancing customer interactions.We are rapidly expanding and seeking passionate innovators eager to solve challenging technical problems, work swiftly, and make a tangible impact at one of the fastest-growing voice AI startups. Join us in shaping the future.Recognized as a top 50 AI app in a16z's list: https://tinyurl.com/5853dt2xRanked #4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025Listed among the top-ranking startups at: https://leanaileaderboard.com/About the RoleAs the Support Engineering Lead at Retell, you will be responsible for overseeing the technical support operations of our sophisticated voice AI platform. This hands-on leadership position involves directly troubleshooting complex customer challenges, developing AI agents and automations, and leading an expanding team of support engineers.You will work at the intersection of engineering, customer relations, and product development, ensuring unparalleled reliability, swift issue resolution, and scalable support systems as Retell continues its growth trajectory.This position is perfect for individuals who thrive on resolving intricate technical issues under pressure, engaging with clients directly, and constructing systems and teams from the ground up.

Join Our Team at Retell AIAt Retell AI, we are pioneering the future of call centers with innovative voice AI technology. In just 18 months, our cutting-edge AI voice agents have transformed how thousands of companies handle their sales, support, and logistics calls, reducing reliance on extensive human teams. Supported by renowned investors such as Y Combinator and Alt Capital, we have achieved remarkable growth, scaling from $5 million to $36 million in annual recurring revenue (ARR) with a dedicated team of 20.Our ambitious vision for 2026 is to develop a comprehensive customer experience platform powered entirely by AI. We are redefining automation by building intelligent AI agents capable of functioning as frontline representatives, quality assurance analysts, and managers, ensuring continuous improvement in customer interactions.As we expand, we seek passionate innovators eager to tackle challenging technical problems and make a significant impact at one of the fastest-growing startups in voice AI. Together, let’s shape the future.Recognized as a top 50 AI application in the a16z list: https://tinyurl.com/5853dt2xRanked #4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025One of the top startups on: https://leanaileaderboard.com/About the RoleWe are looking for a Senior Product Designer to craft exceptional products at Retell. You will design the infrastructure and tools that enable real-time AI voice agents used by dynamic companies. The quality of design is paramount as every interaction occurs in real time, with actual users under pressure.In this role, you will take ownership of end-to-end product design across essential user workflows. Collaborating closely with founders, engineers, and customers, you will shape features from the ground up, rather than merely refining existing user interfaces. This position offers substantial ownership and influence over product direction, user experience quality, and design standards.

Join Us at Retell AIRetell AI is revolutionizing the call center industry by leveraging innovative voice AI technology based on first principles.In just 18 months since our inception, we have attracted thousands of companies that rely on Retell's AI voice agents to efficiently manage sales, support, and logistics calls, previously handled by large teams of human agents. Supported by renowned investors such as Y Combinator and Alt Capital, we have rapidly grown from $5M to $36M in Annual Recurring Revenue (ARR) with a dedicated team of 20.Looking ahead to 2026, our ambition is to establish a state-of-the-art customer experience platform entirely powered by AI. We aim to create intelligent AI “workers” capable of serving as frontline agents, quality assurance analysts, and managers, continuously optimizing customer interactions without the need for constant human oversight.We are on an exciting growth trajectory and are seeking driven individuals who are eager to solve complex technical challenges, accelerate progress, and make a significant impact at one of the fastest-growing voice AI startups.Let’s innovate the future together!Ranked as a top 50 AI app by a16z: https://tinyurl.com/5853dt2x#4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025One of the top startups on: https://leanaileaderboard.com/

Join Retell AI as a Senior Full Stack Software EngineerAt Retell AI, we are revolutionizing the call center industry with innovative voice AI technology. Our cutting-edge solutions are designed to improve communication efficiency, allowing businesses to automate sales, support, and logistics calls that once required large teams of human agents. In just 18 months, we have experienced remarkable growth, achieving $36M in annual recurring revenue with a dedicated team of 20, up from $5M at the beginning of 2025.Our goal for 2026 is to create a modern customer experience platform powered entirely by AI. We are not just automating but building intelligent AI agents that can perform the roles of frontline agents, quality assurance analysts, and managers, continuously enhancing customer interactions.We are rapidly expanding and seeking talented individuals who are ready to solve challenging technical problems, work at a fast pace, and make a significant impact in one of the fastest-growing voice AI startups.Let’s shape the future of communication together!

About Liquid AIBorn from the innovative environment of MIT CSAIL, Liquid AI develops cutting-edge general-purpose AI systems that operate seamlessly across various deployment environments—from data center accelerators to on-device hardware. Our solutions prioritize low latency, minimal memory consumption, privacy, and reliability. We collaborate with leading enterprises in sectors such as consumer electronics, automotive, life sciences, and financial services. As we experience rapid growth, we are eager to welcome exceptional talent to our dynamic team.The OpportunityJoin us in establishing the product function that will transform Liquid AI's technological advancements into scalable, repeatable solutions for enterprise clients. As a key member of our Product team, you will work closely with technical leaders to define, package, and launch AI solutions that meet market needs. This role requires daily collaboration with ML engineers, GTM leaders, and enterprise customers to understand the value of our technology and effectively deliver it. This position offers significant ownership, allowing you to treat your solution area like your own startup within our organization.What We're Looking ForWe are seeking an individual who embodies the following qualities:Customer Obsession: Prioritizes understanding customer needs through direct feedback rather than assumptions.Self-Direction: Takes initiative to dive deep into problems without prompting, and is comfortable navigating uncertainty to propose effective solutions.Technical Fluency: Engages confidently with ML engineers and researchers, understanding the complexities of deploying AI systems in real-world applications.Founder Mentality: Treats their solution area as a startup, owning outcomes across various functions, from technical architecture to go-to-market strategies.The WorkOversee one or more go-to-market ready solutions from inception to scalable customer deployment.Analyze customer interactions to extract insights and identify productization opportunities.Collaborate with ML and inference teams to develop tools that streamline implementation.Define Ideal Customer Profiles (ICPs), pricing strategies, and packaging for scalable solutions.Partner with GTM teams to enhance outbound sales efforts around productized offerings.

Role OverviewLocation: San Francisco, CA Work Model: In-officeAbout Effective AIAt Effective AI, we are pioneering the future of work, focusing on sophisticated AI solutions for complex knowledge tasks rather than simple, repetitive functions. Our goal is to develop advanced AI Teammates that excel in intricate workflows and collaborate seamlessly with human professionals. Our initial challenge is to revolutionize the trillion-dollar U.S. Property & Casualty insurance sector, an area rich in data and complexity, ideal for our innovative approach.We have successfully secured $10 million in seed funding from prominent investors including Lightspeed Ventures and Valor Equity Partners.Our passionate team operates out of San Francisco, where we value in-person collaboration to address these pressing challenges.Your ResponsibilitiesAs a Founding Software Engineer, you will be an integral member of our founding team, significantly influencing the design and development of our core product from inception. You will confront critical challenges in agentic AI, crafting Teammates capable of managing essential insurance functions such as underwriting and claims processing.Specifically, you will:Facilitate long-term task completion by creating the foundational architecture for AI agents to plan and execute multi-step processes reliably over prolonged interactions.Develop advanced reasoning functionalities, enabling agents to make informed decisions based on ambiguous or incomplete information, akin to human experts.Create intelligent, tool-utilizing agents capable of selecting and employing a variety of external tools—APIs, databases, web searches, and Excel-based pricing algorithms—to gather information and take decisive actions.Design adaptive and learning systems, equipping our AI Teammates to learn from feedback and adjust to evolving conditions such as regulatory changes or market dynamics.Your ProfileWe seek an innovative and driven builder excited to tackle substantial challenges.You possess a solid foundation in computer science and remarkable problem-solving capabilities, evidenced by impactful projects or previous experience.Your genuine enthusiasm for AI fuels your passion for tackling complex issues.

Overview: Join Listen Labs as our Founding Product Manager, where you will take ownership of essential product components that enhance the user experience from start to finish. You will be instrumental in defining how teams formulate inquiries, how AI conducts and manages research, and how insights are transformed into actionable, decision-ready outputs. Working in a dynamic 0 to 1 environment, you will collaborate closely with engineering, design, research, and go-to-market teams to bring a visionary product to life that scales effectively.This role is perfect for an individual with a strong sense of ownership, eager to create a foundational product at the crossroads of artificial intelligence, customer research, and pragmatic decision-making.About Listen Labs: Listen Labs is an innovative AI-powered research platform designed to help teams gather insights from customer interviews in a fraction of the time it typically takes. Our platform enables users to analyze conversations, identify key themes, and make informed product decisions swiftly.Why Join Us:Exceptional Team: Our team comprises seasoned entrepreneurs with previous AI exits, and talented professionals from renowned companies such as Jane Street, Twitter, Stripe, Affirm, Bain, Goldman Sachs, and other Sequoia-backed startups.Rapid Growth: As a 40-member team funded by Sequoia, we have surged from $0 to a $14M run-rate in less than a year. We prioritize speed, craftsmanship, and collaboration with driven individuals.Strong Market Presence: We are experiencing swift expansion across various sectors, with notable enterprise clients including Google, Microsoft, Nestlé, and Procter & Gamble.Outstanding Performance: Our differentiated product boasts an industry-leading win rate, showcasing our competitive edge.Market Validation: We consistently secure clients across all segments, achieving significant contracts that foster rapid growth.Viral Product: Our interviews reach tens of thousands, driving product-led growth and attracting daily inquiries from Fortune 500 companies.

About TierZero TierZero helps engineering teams operate more effectively in the AI era. The platform supports teams managing code in production, aiming to close the gap between human decision-making and machine capabilities. TierZero improves incident response, increases operational visibility, and encourages sharing of knowledge within teams. With $7M in funding from investors including Accel and SV Angel, TierZero works with companies like Discord, Drata, and Framer to optimize their large-scale systems. Role Overview: Founding Product Designer This San Francisco-based role is the first product design hire at TierZero. The designer will work closely with the CEO, CTO, and engineering teams, and will be in direct contact with customers to gather insights and feedback. The position blends design with system thinking, with a focus on building trust and supporting better operator decisions. What You Will Do Design core workflows and dashboards for AI agents handling incidents and production issues. Translate complex system behaviors into clear, dependable user experiences. Develop safety guardrails and interaction patterns that make automation predictable and reversible. Work closely with engineers to shape product decisions and defaults, going beyond visual design. Create high-density, high-signal interfaces for engineers working under pressure. Define how people interact, supervise, and collaborate with AI agents. Build interaction models for extended, multi-step agent workflows. Iterate quickly based on customer feedback from real incidents and on-call scenarios. Contribute to many areas of the company, including product direction, sales presentations, and office culture. Why Join TierZero? Work with a seasoned team, including a CEO with multiple startups behind them and a CTO with deep AI engineering experience. Join a company that values input and creativity, where every team member shapes the work environment.

About Simple AIAt Simple AI, we are pioneering cutting-edge voice AI solutions tailored for enterprises. Our lifelike voice agents empower renowned companies such as DoorDash, xAI, and Omaha Steaks in managing diverse phone operations ranging from customer support to order intake and lead qualification. As we experience rapid revenue growth, we seek a couple of founding software engineers to help us meet current customer demands while developing innovative systems for the future. Our team is passionate about harnessing AI to transform the world, and we operate from our San Francisco office five days a week.Simple AI is proudly supported by top-tier investors and industry leaders, including Y Combinator, Massive Tech Ventures, and prominent figures like Michael Seibel (co-founder of Twitch), Jared Friedman (Scribd), Alexandr Wang (Scale AI), Matt Van Horn (June Oven and Lyft), Suhail Doshi (Mixpanel), JJ Fliegelman (WayUp), and Scott Wu (Cognition).Meet the FoundersThe founders, Catheryn Li and Zach Kamran, previously led software teams at Y Combinator, where they launched numerous products for YC founders, including the co-founder matching site. Cat brings experience from Instagram and Facebook and holds degrees in mathematics and computer science from MIT. Zach studied computer science and statistics at the University of Chicago and led software initiatives at PEAK6.What We ProvideCompetitive salary with significant equity opportunitiesEmployee-friendly equity termsOffice located in San FranciscoComprehensive health, dental, and vision insuranceComplimentary lunch and dinner at the officeFree Uber rides home after 8:30 PMRegular team events and offsite activitiesYour Qualifications4+ years of relevant software engineering experience.Exceptional problem-solving skills and a passion for tackling technical challenges.A customer-centric mindset coupled with strong communication skills and a keen interest in product design and prioritization.Self-motivated with the ability to work independently.A genuine enthusiasm for continual learning and keeping abreast of the latest advancements in AI.

Join Thorin as a Founding Product Manager!As a pioneering member of our team, you will play a pivotal role in shaping the future of applied AI solutions that redefine productivity in modern organizations.At Thorin, we leverage cutting-edge AI technology to create proactive agents that continuously monitor and optimize workflows across platforms like Slack, email, and meetings, ensuring that no task falls through the cracks.Our approach goes beyond traditional AI tools; we build real-time digital twins of organizational processes, enabling seamless automation and actionable insights over extended timeframes.With the visionary guidance of Joe Lonsdale and the backing of 8VC, Thorin is set to become a cornerstone of AI-driven productivity.

Join Shiplight AI as a Founding Engineer, AIAre you ready to be at the forefront of the AI revolution and make a significant impact?Do you believe in enhancing productivity exponentially through innovative solutions?At Shiplight AI, we are on a mission to redefine enterprise-scale automation through intelligent agents. We envision a future where organizations leverage AI systems capable of understanding context, taking meaningful actions, and seamlessly collaborating with humans — transforming workplace dynamics.Our initial goal is to revolutionize software quality assurance. We are developing cutting-edge agentic QA systems that integrate deeply within the software development lifecycle, empowering every product manager, developer, and tester with their own AI QA engineer for real-time validation of their work.You will be part of a small, dedicated founding team led by industry experts, focusing on the intersection of AI agents, systems engineering, and enhancing real-world developer productivity.

ABOUT RETELL AIRetell AI is at the forefront of revolutionizing call centers with innovative voice AI technology, utilizing first principles to redefine customer interactions.In just 18 months since our inception, thousands of companies have adopted Retell's AI voice agents to manage sales, support, and logistics calls that previously required extensive human teams. Supported by prestigious investors such as Y Combinator and Alt Capital, we have rapidly scaled to $36M ARR with a lean team of 20, up from $5M at the start of 2025.Our vision for 2026 is to create a modern customer experience (CX) platform where entire contact centers are powered by AI, moving beyond basic automation that relies on constant human intervention to intelligent AI “workers” that operate as frontline agents, quality assurance analysts, and managers, continuously executing, monitoring, and enhancing customer interactions.As we grow, we seek passionate builders eager to tackle challenging technical problems, accelerate progress, and make a genuine impact within one of the fastest-growing voice AI startups.Join us in shaping the future.Ranked among the top 50 AI applications in a16z's list: https://tinyurl.com/5853dt2x#4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025Also recognized as a top-ranking startup on: https://leanaileaderboard.com/ABOUT THE ROLEAs a Senior Software Engineer - Support Automations at Retell, you will take charge of the technical support for our advanced, agentic voice AI platform. This hands-on leadership role involves personally troubleshooting complex customer issues, developing AI agents and automations, and guiding a growing team of support engineers.You will work at the intersection of engineering, customer relations, and product development, ensuring exceptional reliability, swift resolutions, and scalable support as Retell expands.This position is perfect for someone who thrives on solving intricate technical challenges in high-pressure environments, engages directly with customers, and enjoys building systems and teams from the ground up.

Role overview retell-ai seeks a Senior Software Engineer in the San Francisco Bay Area to focus on Go-To-Market (GTM) projects. This engineer will help shape how new products are created and introduced to customers, directly influencing the company’s approach to launching and scaling offerings. What you will do Collaborate with teams across the organization to translate business needs into software that advances GTM objectives. Develop and improve products to ensure they fit seamlessly into the market. Uphold high standards for code quality and system performance as products grow and change. Collaboration This position works closely with product, business, and engineering partners to deliver solutions that address both technical and market demands.