Senior Software Engineer, Infrastructure at Retell AI | San Francisco

At Crusoe, we are on a mission to accelerate the convergence of energy and intelligence. We are building a powerful engine that enables individuals to innovate boldly with AI, all while upholding principles of scalability, speed, and sustainability.Join us in spearheading the AI revolution through sustainable technology. At Crusoe, you will be at the forefront of meaningful innovation, making a significant impact while collaborating with a team dedicated to shaping the future of responsible, transformative cloud infrastructure.About the Role:As a Senior Software Engineer on the Model Lifecycle team, you will play a pivotal role in developing a managed platform that supports the entire application development lifecycle, with an emphasis on harnessing the power of Machine Learning models, particularly Large Language Models (LLMs).Your Responsibilities:Design and maintain systems for fine-tuning large foundational models (SFT, PEFT, LoRA, adapters), ensuring multi-node orchestration, checkpointing, failure recovery, and cost-effective scaling.Create and manage end-to-end training pipelines for Large Language Models.Implement components for distillation and reinforcement learning pipelines, focusing on preference optimization, policy optimization, and reward modeling.Develop and sustain the core agent execution infrastructure.Implement features for dataset, model, and experiment management, emphasizing versioning, lineage, evaluation, and reproducible fine-tuning.Collaboration and Impact:Collaborate closely with Senior Engineers, Principal Engineers, and various product and platform teams to implement systems abstractions and APIs.Engage in technical discussions surrounding training runtimes, scheduling, storage, and overall model lifecycle management.Bring 4-5+ years of industry experience, demonstrating a strong track record of successfully leading a diverse portfolio of initiatives.Participate in and contribute to the open-source LLM ecosystem.This position involves taking significant ownership of core system components.Your Qualifications:Engineering Fundamentals:Bachelor's degree in Computer Science, Engineering, or a related discipline.Proven experience in software engineering with a focus on AI models and machine learning.

Crusoe seeks a Senior Director of AI Model Lifecycle to lead strategy and daily operations for managing AI models in San Francisco, CA. This position plays a central role in shaping how AI models are created, deployed, maintained, and eventually retired. The focus remains on ensuring technical efforts align closely with business priorities. Key responsibilities Define and guide the overall strategy for managing the full lifecycle of AI models Supervise the development, deployment, and ongoing maintenance of AI models Align AI model initiatives with Crusoe’s broader business objectives Identify and implement improvements that increase the impact of AI-driven projects Location This position is based in San Francisco, CA.

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/

AI Financial Modeling Extern — F2 AILocation: San Francisco, CA / In-Person or RemoteCommitment: 5+ hours per week | 4 - 12+ weeksCompensation: $50/hrAbout F2 AIAt F2 AI, we are revolutionizing private market investments. Our cutting-edge AI technology streamlines the process of analyzing complex, unstructured deal materials, transforming them into actionable, investment-grade insights in mere minutes. By empowering private credit funds, commercial banks, and private equity firms, we enable faster and more confident capital deployment. Supported by top-tier investors such as NFX and Y Combinator, we are committed to expanding our exceptional product and engineering teams, shaping the future of vertical AI for finance.Role OverviewWe are on the lookout for 1–2 exceptional externs with a strong foundation in Investment Banking or Private Equity to contribute to the development of AI-driven financial modeling on the F2 platform.In this role, you will collaborate closely with our Engineering, Product, and Design (EPD) teams in the San Francisco office to translate institutional-level financial modeling standards into automated, intelligent workflows. This hands-on experience will allow you to shape the future of AI in financial modeling.Key ResponsibilitiesEducate F2 agents on best practices for financial modeling.Create and standardize financial modeling templates optimized for AI execution using a first principles approach.Establish formatting, structure, and best practices that align with institutional modeling standards.Conduct rigorous quality assurance on AI-generated outputs to guarantee precision that meets investor expectations.Test edge cases and assist in identifying potential failures in automated modeling workflows.Ideal Candidate ProfilePossess prior experience in Investment Banking, Private Credit, or Private Equity with extensive exposure to financial modeling.Demonstrated ability to build and audit complex 3-statement, LBO, or credit models from the ground up.Strong understanding of model hygiene, structure, and institutional formatting standards.Critical thinker who enjoys analyzing model logic and stress-testing systems.Passionate about leveraging AI to enhance financial workflows.

Responsibilities:Develop Our Product. Take ownership of software features that enhance our AI platform, empowering private market investors to analyze deals swiftly and accurately. This role requires you to actively engage in coding and delivering essential platform components from the ground up.Ensure Quality and Excellence. Establish and maintain coding standards, architectural guidelines, and review procedures; mentor fellow engineers. Co-cultivate a culture centered on practical, reliable, and test-driven development that swiftly meets business requirements.Scale for Growth. Assist in monitoring and scaling the architecture of our platform and its infrastructure.Collaborate Across Functions. Engage closely with product, security, and go-to-market teams to translate our strategic roadmap into actionable features and deliverables.

As a Senior Staff Software Engineer specializing in Model LifeCycle at Crusoe, you will play a vital role in shaping the future of software solutions that optimize and enhance our innovative operations. You will lead complex projects, mentor junior engineers, and collaborate with cross-functional teams to deliver high-impact results.

fractional-ai is looking for a Senior or Staff Software Engineer to join the San Francisco office. This position centers on building advanced AI solutions with a team that values both technical depth and collaboration. Role overview This role focuses on designing and developing AI-driven systems. The work involves solving technical challenges and contributing to projects that push the boundaries of what AI can achieve. Collaboration with other engineers and stakeholders is a key part of daily responsibilities. Who will thrive Experienced engineers with a strong background in software development Those who enjoy working on complex technical problems Individuals who value teamwork and open communication Location This position is based in the San Francisco office.

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 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 Us in Combating the Escalating Wildfire Crisis with Cutting-Edge AI and IoT SolutionsAbout UsThe Challenge: In the face of climate change, wildfires are becoming more frequent and severe. Traditional methods of fire detection, reliant on bystanders and emergency calls, lead to critical delays in response times. Fire authorities require innovative solutions for faster detection, verification, and response to avert catastrophic fire outbreaks.Who We Are: Pano AI is a dynamic growth-stage startup based in San Francisco, comprising over 150 passionate professionals. We stand at the forefront of wildfire detection and intelligence, equipping fire services with timely information and advanced technology to enhance their response capabilities. Our platform integrates cutting-edge hardware, software, and AI, utilizing ultra-high-definition 360-degree cameras positioned strategically to provide real-time threat assessments. Our technology empowers fire professionals with actionable insights, enabling them to prevent minor flare-ups from escalating into significant disasters.Recognized by TIME as one of the 100 Most Influential Companies of 2025, and featured in MIT Technology Review's top 15 climate tech companies to watch, Pano AI is paving the way for innovative solutions in fire response. Our contributions have been recognized in major publications such as the Wall Street Journal and Bloomberg.

ABOUT BASETENAt Baseten, we are at the forefront of enabling transformative AI solutions for some of the world's leading companies, including Cursor, Notion, OpenEvidence, Abridge, Clay, Gamma, and Writer. Our innovative platform combines cutting-edge AI research, adaptable infrastructure, and developer-friendly tools to facilitate the production of advanced models. Recently, we celebrated our rapid growth with a successful $300M Series E funding round from notable investors like BOND, IVP, Spark Capital, Greylock, and Conviction. We invite you to join our dynamic team and contribute to the evolution of AI product deployment.THE ROLEAs a Senior Software Engineer specializing in Model Training at Baseten, you will play a pivotal role in constructing the infrastructure essential for the large-scale training and fine-tuning of foundational AI models. Your responsibilities will include designing and implementing distributed training systems, optimizing GPU utilization, and establishing scalable pipelines that empower Baseten and our clientele to adapt models with efficiency and reliability. This role demands a high level of technical expertise and hands-on involvement: you will be responsible for critical components of our training stack, collaborate with product and infrastructure teams to identify customer needs, and drive advancements in scalable training infrastructure.EXAMPLE WORK:Training open-source models that surpass GPT-5 capabilities for a leading digital insurerExploring specialized, continuously learning models as the future of AIOverview of our training documentationResearch initiatives we've undertakenRESPONSIBILITIESDesign, construct, and sustain distributed training infrastructures for large foundation modelsDevelop scalable pipelines for fine-tuning and training across diverse GPU/accelerator clustersEnhance training performance through optimization of algorithms and infrastructureCollaborate closely with cross-functional teams to align technical solutions with business objectivesStay abreast of advancements in the field of machine learning and AI to continually improve our training processes

At Databricks, we are dedicated to empowering data teams to tackle some of the most challenging issues of our time—from realizing the future of transportation to speeding up medical innovations. We achieve this by developing and maintaining the premier data and AI infrastructure platform, allowing our clients to leverage profound data insights to enhance their operations. Our Model Serving product equips organizations with a cohesive, scalable, and governed platform for deploying and overseeing AI/ML models, spanning traditional ML to specialized large language models. It provides real-time, low-latency inference, governance, monitoring, and lineage capabilities. With the rapid rise of AI adoption, Model Serving stands as a fundamental component of the Databricks platform, enabling clients to operationalize models efficiently and cost-effectively at scale. As a Senior Engineer, your role will be pivotal in transforming both the product experience and the underlying infrastructure of Model Serving. You will design and create systems enabling high-throughput, low-latency inference across CPU and GPU workloads, influence architectural strategies, and work closely with platform, product, infrastructure, and research teams to deliver an exceptional serving platform.

The Trade Desk is a leading global technology company dedicated to fostering a better, more open internet for everyone through principled, intelligent advertising. With the capability to handle over 1 trillion queries daily, our platform operates at an unparalleled scale. We pride ourselves on our award-winning culture, built on the foundations of trust, ownership, empathy, and collaboration. We appreciate the unique experiences and perspectives that every individual brings to The Trade Desk, and we are committed to creating inclusive spaces where everyone can express their authentic selves at work. If you are passionate about solving complex problems at scale and are eager to join a dynamic, globally-connected team where your contributions will significantly impact the media ecosystem, we invite you to explore why Fortune magazine consistently ranks The Trade Desk among the top small to medium-sized workplaces worldwide. As a Senior Software Engineer, you will have end-to-end ownership, allowing you to engage in various facets of designing, building, and delivering data-centric products for our stakeholders. At The Trade Desk, we focus on constructing the back-end infrastructure of our platform with an unwavering commitment to quality at scale. Whether developing components for our client-facing applications, crafting internal custom solutions for our teams, or building model pipelines for bidding optimizations, we ensure that the infrastructure, development processes, and tools empower us to execute efficiently. Our systems operate continuously, serving global traffic, and we collaborate in a highly cooperative environment while leveraging a diverse array of technologies. Our back-end developers tackle algorithmic, optimization, and scalability challenges across all our initiatives.

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 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.

Employee Applicant Privacy NoticeWho We Are:Join us in shaping a brighter financial future.At SoFi, we are transforming the personal finance landscape and empowering our members to achieve their financial goals through innovative, mobile-first technology. As a next-generation financial services company and national bank, we are at the forefront of an unprecedented industry transformation. Our core values guide us daily, and we take pride in the meaningful impact we have on our members' lives. Invest in yourself, your career, and the financial world with us.The Role:We are seeking a seasoned Senior Staff Software Engineer to join our Builder Tools engineering team. This role involves enabling SoFi engineers to effectively address challenges by influencing the architecture and direction of our next-gen AI-powered Software Development Lifecycle (SDLC). You will enhance developer experience through AI-enabled workflows, tooling, and practices, while leading and tackling intricate problems in a dynamic, collaborative environment. The ideal candidate will be a mentor, a technical leader, and a team player, hands-on in driving solutions from architecture through to implementation with a strong sense of ownership and commitment to delivery.What You’ll Do:Technical Leadership: Provide guidance on technical architecture and design, implementation, delivery, and operations of AI-enabled tools across the SDLC including planning, coding, testing, building, deploying, observing, and remediating.Innovate: Collaborate with cross-functional teams to foster innovation in developer tooling and advancements, including AI-assisted productivity flows.Exemplary Practitioner: Serve as a subject matter expert in one or more developer tooling domains, ensuring operational excellence.Mentor: Work closely with team engineers, providing mentorship and domain expertise to bolster the team's overall technical capabilities.

fractional-ai is hiring a Software Engineer to join the team onsite in San Francisco. This role centers on building and improving technology that advances artificial intelligence. Role overview As a Software Engineer, you will work closely with others to develop and support projects that drive the company’s AI initiatives forward. The work involves collaborating with colleagues and contributing technical solutions in a team setting. What you will do Develop software for AI-driven projects Collaborate with team members in the San Francisco office Contribute ideas and technical expertise to ongoing initiatives Requirements Interest in technology and artificial intelligence Ability to work onsite in San Francisco Strong motivation to learn and contribute to team projects

About Scale AIAt Scale AI, we are dedicated to revolutionizing the development of artificial intelligence applications. For eight years, we have established ourselves as the foremost AI data foundry, driving groundbreaking advancements in areas such as generative AI, defense applications, and autonomous vehicles. With our recent Series F funding round, we are poised to enhance the availability of frontier data, paving the way towards Artificial General Intelligence (AGI). Our commitment extends to refining our model evaluation expertise for enterprise clients and government entities, thereby enriching our capabilities for both public and private assessments.About the Generative AI Data EngineOur Generative AI Data Engine empowers the most sophisticated LLMs and generative models through premier Reinforcement Learning with Human Feedback (RLHF), human data generation, model evaluation, safety, and alignment. The data we generate is pivotal for shaping humanity's interaction with artificial intelligence.Our ApproachDuring the interview process, candidates may be considered for various roles across different teams within the GenAI Engineering organization based on their skills, interests, and business needs. Potential placements include Allocation, Growth, Frontier Data, Trust & Safety, Pay, Operator, or Tasking Experience. These teams are instrumental in scaling Scale AI’s operations - from curating impactful datasets that enhance LLM capabilities to optimizing contributor onboarding and ensuring data integrity through advanced safety and security protocols. They operate at the crossroads of machine learning, operations, and analytics to guarantee that we deliver top-tier data at scale.Key Responsibilities:Design, develop, and maintain robust, scalable systems across the entire stack, including front-end, back-end, and infrastructure.Implement high-impact features using contemporary technologies such as TypeScript, React, Node.js, MongoDB, Elasticsearch, and Temporal.Work collaboratively with internal operators to identify bottlenecks and deliver rapid, effective solutions.Take ownership of core systems crucial to our contributor platform, directly influencing Scale’s GenAI data pipeline and overall business outcomes.Architect and scale infrastructure to manage millions of tasks weekly with high reliability and low latency.Collaborate cross-functionally with ML teams, Forward Deployed Engineers, and Product to maintain data quality and operational excellence.Contribute to fostering a robust engineering culture while setting best practices for peers through mentorship, code reviews, and process improvement.

Join Our Innovative Team at ArcadeAt Arcade, we are revolutionizing the way physical products are created with our cutting-edge AI platform. We empower individuals to turn their creative ideas into tangible products seamlessly, utilizing natural language and generative AI. Our mission is to democratize product design, making it as effortless as sharing a post online.Backed by a remarkable $42M in funding from industry-leading investors including Reid Hoffman and Ashton Kutcher, our company is a rising star in the tech landscape. Guided by our founder Mariam Naficy and a team steeped in AI and design expertise, we are at the forefront of a new frontier that merges AI, personal expression, and on-demand manufacturing.Your Role as an Applied AI EngineerWe are on the lookout for an Applied AI Engineer to enhance our generative AI capabilities. This position combines hands-on model development with the integration of advanced AI techniques into our production systems. You will collaborate with diverse teams to conduct research, experiment with models, and implement AI-driven products.