Senior or Staff AI Infrastructure Engineer

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.

Employee Applicant Privacy NoticeAbout Us:Join us in shaping a brighter financial future!At SoFi, we are transforming the way individuals approach and manage their personal finances. As a next-generation financial services company and national bank, we leverage innovative, mobile-first technology to empower our millions of members in achieving their financial goals. We pride ourselves on being at the forefront of an unprecedented transformation in the industry, knowing that our efforts have a meaningful impact on people's lives. Invest in yourself, your career, and the financial landscape with us!The Opportunity:As a Senior Staff AI Engineer at SoFi, you will play a pivotal role in our independent risk organization. This hands-on position is critical in establishing the technical direction, spearheading execution, and ensuring the successful realization of our most intricate, production-level AI projects. You will be key in conceptualizing, prototyping, and implementing state-of-the-art AI solutions that address risk management and compliance needs.Working closely with the Director of Risk Analytics, you will apply your extensive expertise to tackle our toughest challenges, mentor emerging engineers, and directly link technical advancements to significant business outcomes. This role is essential for our independent risk function as we strive to assist more members in aligning their financial paths.

Quizlet, Inc. supports millions of learners each month by combining cognitive science with advanced machine learning. The platform serves two-thirds of U.S. high school students and half of college students, powering over 2 billion learning interactions monthly. Quizlet’s mission centers on making education more personal and effective for students, professionals, and lifelong learners. The AI & Data Platform team underpins Quizlet’s applied AI initiatives. This group develops and maintains the systems behind personalization, recommendations, the AI Coach, content generation, and emerging agentic experiences. The team oversees the full machine learning model lifecycle: data and feature engineering, training, evaluation, deployment, and inference. Reliability, speed, security, and observability guide their work. Their approach blends managed Google Cloud services, top vendor tools, open-source solutions, and custom internal abstractions to achieve efficient, reliable outcomes. Role overview The Senior Staff Engineer, AI Platform, is a senior individual contributor who defines the technical direction for Quizlet’s next generation of machine learning and large language model infrastructure. This hands-on role involves architecting core platform systems, steering build-versus-buy decisions, and collaborating with teams across Applied AI, Data Science, Product Engineering, and Infrastructure. The position sets standards for how models and LLM-driven systems are trained, evaluated, deployed, and governed at scale. This role is well suited to an engineer who excels at the senior-staff level in large organizations but values the autonomy and impact of a smaller, cloud-native setting. The technology stack includes Google Cloud, Kubernetes and GKE, distributed training, MLflow workflows, data and feature platforms, online and asynchronous inference, and the evaluation and observability tools needed to operate predictive ML and LLM systems at scale. Work location and schedule This is an onsite position based in San Francisco, CA. Team members are expected in the office at least three days a week: Monday, Wednesday, and Thursday, to foster collaboration.

Join Connectly as we revolutionize conversational commerce in Latin America, focusing on the WhatsApp platform. With WhatsApp shopping becoming increasingly prevalent, we are dedicated to creating an AI-driven sales solution tailored for large retailers. Our mission is to streamline the purchasing process by ensuring real human interaction in response to WhatsApp inquiries.As a VC-backed Series B startup, we boast a diverse and talented team hailing from industry giants like Meta, Google, and Uber. Operating in a hybrid work environment, we maintain offices in Bogotá and San Francisco, with teams distributed across Latin America, including Brazil, where many of our innovative AI initiatives are developed.

Join David AI as a Staff Product EngineerAt David AI, we are pioneering the field of audio data research, applying a rigorous R&D methodology to create robust datasets that empower AI models. Our vision is to integrate AI seamlessly into daily life, with audio serving as the key medium. As the demand for high-quality training data grows, we position ourselves as the solution.Founded in 2024 by a team of seasoned engineers from Scale AI, we quickly garnered the trust of leading FAANG companies and AI labs. Our recent $50M Series B funding round was led by prestigious investors including Meritech and NVIDIA, underscoring our potential in the audio AI landscape.We pride ourselves on our dynamic, collaborative, and ambitious team, and we are on the lookout for exceptional talent in research, engineering, product, and operations to help us redefine audio AI.About Our Engineering TeamOur engineering team is at the forefront of innovation, building the infrastructure, platforms, and models that convert raw audio into valuable data for top-tier AI labs and enterprises. We are a close-knit group of product engineers, infrastructure experts, and machine learning specialists who are dedicated to establishing the first-ever audio data research organization.We operate with agility, taking ownership of our projects from inception to deployment, delivering production-ready solutions on a daily basis. Our engineers design real-time pipelines that manage vast amounts of speech data while deploying advanced generative audio models.Your RoleAs a Staff Product Engineer, you will spearhead our Product Engineering team, developing state-of-the-art products that enable our clients to harness audio data effectively for model training. You will collaborate with researchers to continually refine our data collection methodologies.Your ResponsibilitiesLead the development of full-stack features, rapidly iterating to deliver daily innovations to our users.Construct scalable systems that process terabytes of audio data and extract actionable insights.Deploy and assess LLM- and DSP-based solutions to enhance customer understanding of their data.Facilitate research iterations and deployment interfaces for data collection in collaboration with researchers and operations.

About UsXOXO is an innovative research lab dedicated to crafting intelligent interfaces that enhance everyday life. Our stealth team, composed of passionate engineers, designers, and researchers, is focused on solving unique challenges that go beyond the workplace.With recent advancements in infrastructure, architecture, and model layers, we are actively seeking skilled builders to create the application layer that will actualize our visionary concepts.About the RoleWe are on the lookout for a proficient iOS engineer to lead the development of XOXO’s consumer app, featuring a pioneering interface for intelligence. This position calls for a robust engineer capable of managing the entire mobile surface area, from architecture and performance to refining a visually appealing design system that ensures intentional user interactions.A specific background is not mandatory; what truly matters is your passion for ownership: you take charge, work swiftly without compromising quality, and aspire to create a mobile product that redefines craftsmanship and performance standards.What You’ll DoDesign and launch the initial versions of our React Native app, transitioning it from concept to production.Convert a visually rich design system into reusable components, motions, and interaction patterns with seamless performance.Develop new product interfaces that seamlessly integrate modern AI/ML capabilities in a mobile-friendly manner.Enhance app performance, focusing on rendering, startup, memory consumption, battery usage, and perceived speed.Establish high standards for mobile engineering quality (including testing, monitoring, and release management) while collaborating with various teams to ensure successful delivery.

Join Saris AI as a Staff Backend Software Engineer, where you will play a pivotal role in developing innovative solutions that harness the power of artificial intelligence. In this dynamic position, you will collaborate with cross-functional teams, design scalable systems, and contribute to the overall architecture of our backend solutions.

Join Laurel as a Staff AI Platform Engineer, where you will be at the forefront of developing cutting-edge AI platforms that drive innovation and efficiency. In this role, you will collaborate with cross-functional teams to create scalable AI solutions that enhance our products and services.

With support from prominent Silicon Valley investors, Peregrine Technologies empowers public safety organizations, state and local governments, federal agencies, and private sector entities to tackle societal challenges with unparalleled speed and precision. Our AI-driven platform transforms isolated and disparate data into actionable intelligence, rapidly presenting critical information that enables improved decision-making and outcomes. Currently, Peregrine serves hundreds of clients across over 30 states and two countries, impacting more than 125 million individuals, as we broaden our reach into enterprise markets and international territories.TeamOur engineering team is deeply committed to the idea that empathy enhances our solutions. Understanding how users interact with our products is fundamental to our approach. Engineers have the unique opportunity to collaborate closely with our onsite team to grasp the diverse use cases that Peregrine addresses.We cherish both ownership and teamwork; you will be fully accountable for significant features while working hand-in-hand with fellow engineers to ensure successful delivery. We believe that humility and empathy are critical for crafting effective solutions, and you will engage directly with our deployment team and users as we refine our offerings to meet their needs. Ingenuity and perseverance are vital in realizing our vision.RoleAs part of our new AI team, you will play a key role in delivering unique value to our clients. This team is responsible for designing powerful and intuitive user experiences powered by generative AI. You will explore entirely new interaction methods for users—whether through natural language commands or by enabling AI agents to manage complex tasks on their behalf. Your contributions will shape impactful AI-driven features that assist customers in solving real-world challenges more efficiently.Your work will encompass a variety of intricate challenges, including scaling our platform to process terabytes of data from multiple sources, efficiently querying and alerting users about this data in real-time, and optimizing search algorithms for swift result delivery.While our technology stack is continuously evolving, it is built on a foundation that includes Python, Django, Celery, Airflow, and Kafka for the backend; React, Redux, and Mapbox for the frontend; PostgreSQL and Elasticsearch for data storage; machine learning models hosted in Bedrock and Sagemaker; and utilizing AWS, Pulumi, Terraform, and Kubernetes for our infrastructure.

ABOUT RETELL AIAt Retell AI, we are revolutionizing the call center experience using cutting-edge voice AI technology. In just 18 months since our inception, thousands of companies have leveraged our AI voice agents to streamline sales, support, and logistics operations that previously required extensive human teams. Supported by prominent investors such as Y Combinator and Alt Capital, we have grown from $5M to an impressive $36M ARR with a dedicated team of 20.Our ambitious vision for 2026 is to create a state-of-the-art customer experience platform where entire contact centers are driven by AI. Rather than relying on basic automation that necessitates constant human oversight, we are developing intelligent AI “workers” to function as frontline agents, QA analysts, and managers—constantly executing, monitoring, and enhancing customer interactions.As we rapidly expand, we seek passionate innovators eager to solve complex technical challenges, move swiftly, and make a meaningful impact at one of the fastest-growing voice AI startups. Join us in building the future!Ranked among the top 50 AI applications 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 the Leana I leaderboard: https://leanaileaderboard.com/THE ROLEWe are in search of a Principal/Staff Engineer to spearhead the technical direction of our core platform. This is an individual contributor role designed for someone who excels in uncertainty, acts swiftly, and elevates the standards of those around them.You will engage with various systems, infrastructure, and product surfaces while collaborating closely with engineering teams, product managers, and leadership to scale successful initiatives and innovate for the future.This role is not about merely addressing tickets; you will identify challenges, engineer solutions, and deliver impactful results.KEY RESPONSIBILITIESLead the design and evolution of our core platform and systems architecture.Oversee complex technical projects from inception to production.Make strategic technical decisions that optimize for speed, reliability, and scalability.Collaborate across teams to facilitate knowledge sharing and best practices.

Who We Are:TwelveLabs is at the forefront of developing innovative multimodal foundation models that enable video comprehension akin to human understanding. Our groundbreaking models have set new benchmarks in video-language modeling, enhancing our capabilities and revolutionizing how we engage with and analyze diverse media formats.With an impressive $107 million in Seed and Series A funding, we're supported by premier venture capital firms including NVIDIA’s NVentures, NEA, Radical Ventures, and Index Ventures, alongside influential AI pioneers like Fei-Fei Li, Silvio Savarese, and Alexandr Wang. Our headquarters in San Francisco, complemented by a significant presence in Seoul, highlights our dedication to fostering global innovation.We celebrate the individuality of every team member’s journey, believing that the diverse cultural, educational, and life experiences of our employees fuel our ability to challenge the status quo. We seek passionate individuals who resonate with our mission and are eager to make a significant impact as we advance technology to reshape the world. Join us in redefining video understanding and multimodal AI.About the RoleAs a Senior Staff Infrastructure Engineer at TwelveLabs, you will leverage your technical expertise and leadership skills to construct the systems that drive our multimodal foundation models. Your focus will be on designing and enhancing a scalable, secure, and high-performance infrastructure that accommodates extensive AI workloads across both cloud-based and on-premises environments.This position demands strong technical acumen, an eagerness to delve into low-level systems when necessary, and the capability to influence infrastructure strategy through hands-on contributions and operational improvements. Your impact will be felt through your technical expertise and the results you deliver, rather than through hierarchical status, in a dynamic and fast-paced environment.In this role, you will:Architect and advance cloud and hybrid infrastructure, blending hands-on execution with technical leadership.Guide the development of AI/ML infrastructure components, engaging directly in critical tasks when necessary.Define infrastructure standards and abstractions while maintaining close interaction with production systems.Collaborate closely with Machine Learning Engineers, Data Scientists, Backend Developers, and other key stakeholders to ensure system alignment and efficiency.

At Crusoe, we are dedicated to accelerating the abundance of energy and intelligence. As a pioneering AI infrastructure company, we control every aspect of our operations — from energy generation to the digital tokens that power the world’s most ambitious AI workloads. Joining Crusoe means being part of a team that is shaping the future at an unprecedented pace.We are amid a transformative industrial revolution. The endless demand for AI computing power poses significant challenges, particularly concerning energy supply. Our energy-first strategy not only enhances AI infrastructure but also contributes positively to the environment, empowering innovators in the AI sector.We seek proactive, problem-solving team members who recognize the scale of our mission and are eager to navigate uncharted territories. If you aspire to advance your career alongside experts in energy, manufacturing, data center construction, and cloud services, we invite you to become part of our dynamic team.If you are ready to engage in the most impactful work of your career, assist our customers and partners in elevating their AI strategies, and contribute to a high-performing, supportive team, we welcome you to build the future with us at Crusoe.About This RoleThe Cloud Storage team at Crusoe is searching for a Senior Staff Software Engineer to act as the principal architect for our storage strategy. Unlike a Staff Engineer who leads feature development, a Senior Staff Engineer will define the long-term technical roadmap essential for our AI-scale infrastructure. You will play a crucial role in establishing the architectural strategy, ensuring the integrity and global scalability of our specialized storage services. Your work will focus on the underlying physics of the stack, bridging high-performance NVMe hardware with globally distributed object storage solutions that compete with S3.Your ResponsibilitiesArchitectural Vision & Strategy: Lead the development and execution of the long-term technical strategy for Crusoe's storage engine, while identifying and integrating industry trends such as CXL and NVMe-oF into a unified roadmap.System Programming Expertise: Utilize your extensive experience in system programming with languages such as C, C++, Go, and Rust to lay the groundwork for our V2 storage re-architecture.Storage Protocols: Design and implement solutions employing industry-standard storage protocols, including NFS, SMB, iSCSI, and NVMe/TCP.

About ApiphanyApiphany is a trailblazing AI company focused on revolutionizing physical product development. We empower innovators across automotive, aerospace, medtech, and energy sectors to convert vast unstructured technical data into real-time, actionable insights. Supported by elite investors including Markforged, Databricks, GM, and Character, our mission is to transform engineering decision-making, turning complexity into simplicity for leading manufacturers worldwide.Our advanced models are designed to address the intricacies of engineering and manufacturing, comprehending physics principles, design specifications, and program constraints. Our small, elite team consists of builders hailing from prestigious institutions such as Stanford, Berkeley, MIT, UW, and CMU, along with industry veterans from GM, Ford, and Genesis Therapeutics. We are committed to advancing hard-tech and establishing a market-leading company together.About the RoleIn the role of Senior / Staff Infrastructure Engineer at Apiphany, you will architect, build, and manage the infrastructure that underpins our intelligence platform. Your responsibilities will encompass secure, reliable, and scalable cloud deployments, including the unique challenge of deploying across both internal and customer-managed cloud environments.You will ensure our systems adhere to stringent requirements for latency, availability, and compliance within data-intensive environments. Additionally, you will shape our security strategy, implement infrastructure-as-code practices, and establish a solid foundation enabling engineering teams to deliver with assurance.

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/

Role overview MidiHealth is hiring a Staff Software Engineer - AI Engineer for a hybrid role in the San Francisco Bay Area. The position focuses on building and improving AI-powered solutions that contribute to better healthcare outcomes. What you will do Collaborate with cross-functional teams to design and implement AI-driven systems for healthcare. Develop scalable architectures and write efficient algorithms tailored to healthcare applications. Uphold strong software quality standards throughout the development lifecycle. Location This position is hybrid, with work based in the SF Bay Area.

About SpotOnAt SpotOn, we are revolutionizing the restaurant industry by providing independent restaurants with cutting-edge technology to thrive in a competitive market. From our award-winning point-of-sale systems to advanced AI-driven profit enhancement tools, every solution we offer empowers operators to increase profitability, optimize operations, and retain top talent. Our commitment to our clients is backed by a dedicated team that genuinely cares about their success.Ranked #1 Restaurant POS by G2 (Fall 2025), based on user feedbackRecognized as the top-rated point-of-sale (POS) for restaurants, bars, retail, and small businesses by Capterra usersHonored as a Great Place to Work and recipient of Built In’s Best Workplaces awards for consecutive yearsWe prioritize agility, empathy, and advocacy for independent restaurant operators, allowing them to focus on their passion. If you aspire to make a meaningful impact with dedication and drive, SpotOn is your ideal workplace.About the Accelerate TeamThe Accelerate team, consisting of five skilled engineers, is dedicated to redefining software development within the fintech realm through AI-native engineering practices. With direct support from senior leadership and defined project goals, we are committed to setting new industry standards in software building.We are seeking a Staff/Principal Individual Contributor (IC) with proven experience in AI-assisted engineering at scale. This is not a role for the AI-curious; you are someone who integrates AI into coding daily. You have developed agents that deliver tangible results. Your insights on model selection, agent limitations, and effective guardrails are backed by real-world experience. You are eager to apply what you’ve learned on a larger scale.As the most senior technical AI expert on the team, you will be the go-to person for architectural guidance, tackling complex challenges, and establishing technical benchmarks.The Role: Technical Lead, Not ManagerThis position is not about merely setting up CI/CD pipelines or integrating Copilot. You are the architect behind the systems that transform how SpotOn engineers develop software. You will:Establish yourself as the technical authority in AI engineering. You will define the standards for AI utilization in code generation, review, testing, and task automation. Your focus will be on designing systems, workflows, and guardrails that ensure AI-aided development is safe, measurable, and scalable in a PCI-compliant environment.

Join Collective Health as a Staff AI Engineer, specializing in Agentic AI and Automation. In this pivotal role, you will lead innovative projects that leverage artificial intelligence to enhance health management solutions. Collaborate with cross-functional teams to design and implement cutting-edge AI systems, ensuring they align with organizational goals and deliver tangible results.

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.

At Plaid, we envision a future where financial interactions are seamless and intuitive. Our mission is to drive this evolution by crafting powerful tools and experiences that developers leverage to create impactful financial products. With our technology, millions of individuals can manage their finances more effectively. Partnering with renowned companies like Venmo, SoFi, and several Fortune 500 firms, we simplify the process of connecting financial accounts to the applications people depend on. Our network encompasses over 12,000 financial institutions across the US, Canada, the UK, and Europe. Established in 2013, our headquarters is in San Francisco, complemented by offices in New York, Washington D.C., London, and Amsterdam.The advent of AI and intelligent systems marks a pivotal shift in technology, following the eras of mainframes, personal computing, the internet, and mobile devices. We believe that AI will fundamentally transform the FinTech sector—altering consumer finance management, application development, and operational dynamics across businesses.Plaid's Role in the AI-Driven FinTech LandscapePlaid is uniquely positioned to become the backbone of financial data and insights for AI-powered applications in this rapidly evolving FinTech ecosystem.We advocate for consumers to manage their finances effortlessly through conversational AI interfaces. Our commitment extends to ensuring a reliable consent and authorization manager for enhanced privacy and security. We envision a world where identity verification and fraud prevention in AI solutions are seamlessly integrated for users. The demand for such innovations is growing.Leading AI companies, significant fintechs, and customer support platforms are actively integrating Plaid into their AI-driven products and solutions.AI-Enhanced Customer Experiences at PlaidThe rapid advancement of model intelligence presents a unique opportunity for Plaid to reinvent our operations and customer interactions, optimizing the overall experience.Our initial forays into AI-driven customer support have yielded substantial business benefits, demonstrating our commitment to innovative solutions that elevate customer satisfaction.