Senior Full Stack Engineer at gumloop | San Francisco

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!

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

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/

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/

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 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.

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.

About StackAIStackAI is a revolutionary no-code AI workflow platform that enables businesses to construct, implement, and expand AI-driven workflows without requiring extensive machine learning expertise. With a growing user base and increasing enterprise adoption, our goal is to democratize access to large language models (LLMs), empowering every business operator—beyond just developers. Supported by Y Combinator and top-tier investors, we are laying the groundwork for the AI-driven future of work.The RoleAs a Senior Full Stack Engineer, you will be instrumental in defining the product and technical architecture at StackAI. Your responsibilities will span the entire technology stack, from crafting scalable backend systems to creating stunning and user-friendly frontend interfaces, and incorporating advanced AI models into our platform. This role offers significant impact, as you will work closely with the founding team, take charge of essential product features, and shape the engineering culture of a rapidly evolving startup.We seek exceptional 10X engineers—innovative builders who can consistently deliver results in a dynamic environment, remain inquisitive, and excel in diverse roles.ResponsibilitiesIn this role, you will:Build and own the entire platform, from backend services and APIs to frontend interfaces.Create robust, scalable backend systems utilizing Python and FastAPI (or similar), with optimized databases (SQL/NoSQL).Design and maintain high-quality user interfaces using React, Next.js, TypeScript, and Tailwind CSS, ensuring polished, intuitive, and responsive user experiences.Integrate new AI models and features into our products for seamless performance and enhanced value.Manage StackAI’s landing and product pages to establish benchmarks for clarity, design, and quality.Collaborate across the stack to connect backend services with frontend applications seamlessly.Engage with design, product, and customers to refine product direction and prioritize user needs.Stay at the forefront of full-stack technologies, promoting best practices and innovative solutions.Assist with customer support as needed; every team member contributes to user satisfaction.

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/

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.

About HappyRobotHappyRobot is pioneering the AI-native operating system for the real economy—an innovative platform that seamlessly integrates intelligence with actionable outcomes. By harnessing real-time insights, specialized AI agents, and a coordinating intelligence, we empower enterprises to manage intricate, mission-critical operations with genuine autonomy.Our AI OS continuously accumulates knowledge, optimizes processes at every level, and adapts over time. We're initially focusing on supply chain and large-scale industrial operations, where resilience, speed, and ongoing enhancement are paramount—liberating humans to concentrate on strategic thinking, creativity, and other high-value pursuits.Discover more about our vision in our Manifesto. HappyRobot has successfully secured $62M in funding to date, including a recent $44M Series B round in September 2025. Our esteemed investors include Y Combinator (YC), Andreessen Horowitz (a16z), and Base10, who share our commitment to transforming enterprise operations. We are channeling this investment into assembling a world-class team—individuals with unwavering determination, exceptional problem-solving abilities, and a passion for pushing boundaries in a dynamic, high-pressure environment. If this resonates with you, we invite you to join us at HappyRobot.About The RoleAt HappyRobot, Full Stack Engineers take charge of significant components of the product and infrastructure from start to finish.We are seeking creators who thrive in uncertain environments, have a profound appreciation for their craft, and desire authentic ownership over their creations.

About the RoleWe are on the lookout for a skilled Forward Deployed AI Engineer to join our dynamic team at Stack AI. This position is crucial for implementing enterprise-level AI solutions with an emphasis on Retrieval-Augmented Generation (RAG) pipelines and large language model (LLM) workflows. Your contributions will significantly enhance our offerings to Fortune 500 companies and enterprises across diverse sectors.Role Overview:In this role, you will seamlessly integrate large language models into enterprise systems, collaborating with strategic accounts to tailor solutions that meet their technical needs. Utilizing the Stack AI platform, you’ll engage with clients to co-create innovative solutions that address their evolving challenges.Key Responsibilities:Enhance and maintain solutions for strategic accounts using the Stack AI platform.Analyze and document requirements and relationships within target enterprise offices.Identify opportunities and provide insights to shape our go-to-market strategy.Directly contribute to the Stack AI codebase, transforming customer feedback into enhancements for the Python backend and React/Next.js TypeScript frontend.Project future opportunities and secure high-value contracts.Draft proposals, present to stakeholders, and lead engaging product demonstrations.Promote Stack AI at enterprise conferences and events.

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.

ABOUT SPHERESphere is revolutionizing trade compliance with cutting-edge AI technology. Our innovative system, TRAM, autonomously analyzes and interprets global trade laws, ensuring reliable compliance determinations across various jurisdictions. We manage the full compliance lifecycle—from calculation and registration to filing and remittance—with millisecond latency and zero downtime.At Sphere, we are proud to be backed by prominent investors such as a16z and Y Combinator, and we've achieved over 30% month-over-month growth. Our impressive client roster includes emerging leaders like ElevenLabs, Replit, Deel, and Runway. We operate with a small, dedicated team in our San Francisco headquarters, where every member has ownership over significant domains of our platform.THE ROLEWe are seeking experienced Senior Full Stack Engineers to spearhead the development of new product lines, including input tax, withholding tax, e-invoicing, and tariffs. Your contributions will be pivotal in scaling our operations and directly influencing our annual recurring revenue (ARR).WHAT YOU'LL DOWithin weeks:Deliver critical features that clients rely on daily, such as filing infrastructure.Take ownership of a feature and drive measurable outcomes.Collaborate with customers like Eleven Labs, Lovable, and Deel to enhance key components of our platform, aiming to improve filing generation and submission speeds.Within months:Lead the end-to-end development of new product lines, furthering our AI-driven compliance platform.Mentor junior engineers and foster a collaborative team environment.

Join Condor Software as a Full-Stack Platform EngineerAt Condor, we are revolutionizing the financial infrastructure that supports clinical development. With billions invested annually in discovering and developing new therapies, we strive to connect clinical operations and finance into a cohesive system. By integrating real-time financial intelligence, we empower R&D and finance leaders with the tools they need to make informed, high-stakes decisions.We are an AI-driven, pharma-native infrastructure provider, scaling industry standards in collaboration with top-tier partners. Our platform facilitates prediction, control, and execution in the most complex R&D environments worldwide.The Importance of Your RoleHaving established ourselves as a trusted partner for enterprise teams, we are now focused on the challenging task of scaling our platform to meet increasing demands. As a rapidly growing company, backed by prominent investors like Felicis and 645 Ventures, this is a unique opportunity to contribute to the foundational infrastructure that will redefine how therapies reach patients.Your ResponsibilitiesAs a Full-Stack Platform Engineer, you will be pivotal in building and scaling the core platform that supports the financial intelligence infrastructure relied upon by leading biopharma companies. This role encompasses critical engineering tasks at the intersection of backend systems, cloud infrastructure, and intelligent automation, with a strong emphasis on reliability and scalability.Your primary focus will be on backend architecture, where you'll design and implement services that drive complex financial and operational workflows. You'll be instrumental in shaping data flow, workflow orchestration, and enabling emerging AI-driven capabilities. This role goes beyond simple integration; you'll be crafting robust primitives that support other teams as our product and customer base expand.Working as a core member of a cross-functional product team, you will closely collaborate with product managers, designers, quality engineers, and data specialists to transition features from concept to production. While backend expertise is crucial, you will also engage across the stack to ensure the platform's capabilities are effectively leveraged.

Join Binti as a Senior Full Stack Software Engineer and play a crucial role in developing innovative software solutions that enhance our mission to streamline the adoption process. You will be responsible for designing, developing, and maintaining our web applications, ensuring optimal performance and user experience.In this position, you will collaborate with cross-functional teams, participate in all phases of the software development lifecycle, and mentor junior developers. If you are passionate about building scalable applications and are eager to solve complex problems, we want to hear from you!

Why Choose Alex?At Alex, one of the most promising startups emerging from our Y Combinator batch, we are making significant strides in the hiring landscape. We have secured strong funding, are generating revenue, and have ample runway to fuel our growth.Our innovative AI-driven recruitment tool revolutionizes the job interview process, enabling companies to obtain critical hiring insights more swiftly and effectively than ever. Our clients are enthusiastic about our product, and we are just beginning our journey.Who We Are?We are a team of individuals who:Thrive on tackling complex engineering challengesAdapt quickly and are committed to achieving resultsDedicate ourselves to hard workAct with urgencyValue in-person collaboration in our San Francisco office, five days a weekTechnologies We UtilizeWe prefer candidates with experience in:JavaScript (Typescript, React, Node, Next)PythonCloud and DevOps tools (Azure, Kubernetes, Docker)System ArchitectureYour ResponsibilitiesAt Alex, we operate similarly to a marketplace, providing unique interview experiences for candidates and a robust data analysis platform for employers. As a hands-on engineer, you will develop both consumer-facing applications and enterprise-grade software, with ample opportunities for professional growth. Potential consumer software challenges include:How can we reduce average interviewer response latency to 200ms?How can we refine our models to minimize hallucinations and help Alex pass the Turing test?How will our system architecture evolve as we scale to accommodate thousands of users concurrently?You will also address enterprise-related software challenges such as:How do we integrate with our clients' internal hiring systems?What is the optimal way to visually present interview results swiftly?How can Alex facilitate end-to-end coordination of the hiring process?And a myriad of feature requests awaiting your expertise!

At CreatorIQ, we are dedicated to revolutionizing creator-led growth, empowering over 1,300 global brands and agencies to thrive.Our mission is to humanize businesses while amplifying the impact of individuals. Guided by our core values—intentionality, excellence, collective journey, and humanity—we have been recognized as one of the best workplaces by various programs, including BuiltIn LA and NY. Our growth story includes being named one of the Fastest-Growing Companies in North America by Deloitte Technology Fast 500™ for four consecutive years, and being highlighted as a leader in IDC MarketScape: Worldwide Influencer Marketing Platforms for Large Enterprises in 2025, among others. Our flexible work model fosters collaboration and innovation, accommodating diverse working styles.Join us in our exciting journey. Become a vital part of our dynamic team and help transform the industry!Senior Full Stack Engineer, Creator RecruitWe are looking for a talented Senior Full Stack Engineer to enhance our Creator Tools team. Your contributions will significantly improve user experiences and help us develop scalable solutions for our expanding platform.The ideal candidate will possess a strong background in frontend frameworks, solid backend development skills, and a collaborative spirit suited for a fast-paced environment. You should be ready to take ownership of features, contribute to architectural decisions, and maintain high coding standards.The Creator Tools team is responsible for developing all user-facing features on our platform, directly impacting the lives and livelihoods of creators who utilize our tools to earn and sustain their businesses.From payment processing and social authentication to e-commerce solutions and campaign workflows, we enable the full creator experience. Every feature you develop and enhancement you implement is integral to delivering a seamless, intuitive platform that empowers creators to grow and earn with confidence.This role allows you to make an immediate and meaningful difference in the lives of creators who rely on our platform to pursue their passions.