Senior Full Stack Software Engineer at Heidi Health | San Francisco

About UsAt Heidi, we believe healthcare deserves a more harmonious approach—one that ensures care is both ongoing and profoundly human. Our mission is to create an AI Care Partner that collaborates seamlessly with clinicians to achieve this goal.Our diverse team consists of doctors, engineers, designers, researchers, and creatives dedicated to developing too…

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 our dynamic team at Sonsoft Inc. as a J2EE Developer, where you will leverage your expertise in Core Java, Spring Boot, and MAVEN to build robust applications. You will be a crucial part of our development team, contributing to the design and implementation of innovative software solutions that meet client needs.

About the Role:Join our dynamic ML Infrastructure team as a Software Engineer, where you'll collaborate intimately with the Machine Learning and Product teams to construct top-tier machine learning inference platforms. These cutting-edge platforms drive vital services such as personalized recommendations, search functionalities, and content comprehension at Tubi.Your primary focus will be on the development and maintenance of low-latency ML model serving systems that cater to Deep Learning, LLM, and Search models. This will include the creation of self-service infrastructure and critical components such as the inference engine, feature store, vector store, and experimentation engine.In this role, you'll enhance our service deployment and operational processes, with opportunities to contribute to open-source projects. Enjoy architectural freedom to explore innovative frameworks, spearhead significant cross-functional projects, and elevate the capabilities of our ML and Product teams.We are currently hiring for two positions:Staff Software EngineerPrincipal Software EngineerAdditional Details: As a Principal Engineer, you will serve as a technical leader and visionary, guiding the advancement of our machine learning platform. You'll address complex technical challenges, shape architectural decisions, and mentor senior engineers, fostering a culture of excellence and continuous improvement. Your contributions will impact millions of users.

Scale GP is at the forefront of enterprise Generative AI, offering cutting-edge APIs and infrastructure for knowledge retrieval, inference, evaluation, and intelligent automation. We empower critical workflows for leading enterprises, transforming intricate data and models into dependable, production-ready AI systems. Join our newly formed Agentic Data Products team, dedicated to creating the next generation of agent-powered tools that seamlessly integrate AI into real operational workflows. Our mission is to enable enterprises to unravel their data layers and deploy intelligent systems capable of reasoning, acting, and delivering measurable outcomes. This is a pioneering build team, and we are seeking a highly skilled, product-focused Senior Engineer who thrives in dynamic environments, acts swiftly, and relishes the challenge of constructing new systems from the ground up in collaboration with customers and cross-functional teams. You will partner closely with product managers, forward-deployed engineers, data scientists, and applied AI specialists to transform real-world challenges into scalable, production-ready solutions. If you have a passion for rapid delivery, accountability for outcomes, and enjoy working across the entire stack—from sleek front-end applications to robust distributed backends and LLM integrations—this role is perfect for you.

About the Role OpenAI is looking for a Software Engineer specializing in Kernel Performance and AI Tooling to join the team in San Francisco. This role centers on improving software systems for maximum efficiency and building advanced tools that support AI development. What You Will Do Optimize kernel-level performance across OpenAI's software stack. Design and implement tools that accelerate AI research and deployment. Work closely with engineers to identify bottlenecks and deliver practical solutions. Contribute to technical discussions and share knowledge with teammates. Team and Collaboration Work alongside engineers who are committed to advancing AI technology. Collaboration and innovation are central to the team’s approach.

Our mission: to eliminate every barrier to mental health.At Spring Health, we are dedicated to transforming mental healthcare by dismantling every obstacle that hinders individuals from receiving the support they require, precisely when they need it. Our clinically validated technology, Precision Mental Healthcare, empowers us to deliver tailored care—be it therapy, coaching, medication, or more—customized to the unique needs of each individual.We are proud to collaborate with over 450 organizations, ranging from innovative startups to Fortune 500 giants, as a premier provider of mental health services, impacting the lives of 10 million individuals. Our esteemed clients include renowned brands such as Microsoft, Target, and Delta Airlines, who trust us to provide exceptional outcomes for their workforce worldwide. Through our groundbreaking platform, we have achieved a net positive ROI for employers, and we are the sole entity in our field to receive external validation for delivering genuine cost savings to our clients.With significant investments from leading firms like Generation Investment, Kinnevik, Tiger Global, Northzone, RRE Ventures, and more, we have recently completed a Series E funding round, elevating our valuation to $3.3 billion. We are just beginning our journey—join us as we strive to make mental healthcare accessible to everyone, everywhere.In this pivotal role, you will report to the Associate Director of Data Science - Orchestration and spearhead backend systems that facilitate member-provider matching and precision care routing. As a key member of the Orchestration Group, you will play an essential role in translating machine learning and business logic into scalable, reliable production services that enhance member experience, utilization, and margin performance.This is a hybrid position based in San Francisco, with a requirement to be on-site 2–3 days per week at our 2 Embarcadero Center location. Candidates must reside in the San Francisco metro area or be willing to relocate independently within 90 days of their start date. Occasional travel for team gatherings will be necessary.

About UsOur mission is to revolutionize language learning.Learning a new language can transform lives by providing access to diverse cultures, career opportunities, and communities. With two billion people globally striving to learn languages, the most effective method—one-on-one tutoring—remains difficult to access at scale and has not evolved significantly over the years. Speak is developing an AI-powered, human-like tutor that fits in your pocket, offering a conversation-first approach that allows learners to practice speaking, receive immediate feedback, and progress through thoughtfully designed lessons. This results in a comprehensive journey from novice to confident speaker across multiple languages.Since our launch in South Korea in 2019, Speak has emerged as the leading language learning app, now available to learners in various markets and over 15 languages. As one of the foremost AI companies globally, we have secured over $150 million in venture capital from notable investors such as OpenAI, Accel, Founders Fund, and Khosla Ventures, with a diverse team spread across San Francisco, Seoul, Tokyo, Taipei, and Ljubljana.About This RoleWe are seeking a Senior Backend Engineer, with full-stack capabilities, to help create innovative AI-driven product experiences. The ideal candidate should have experience collaborating closely with product, design, and machine learning teams, alongside a proven track record in developing polished consumer applications. This role is pivotal in shaping our latest products focused on programmatic, conversational language learning and will significantly impact the future direction of our company.Your ResponsibilitiesCrafting innovative AI-driven product experiences and user interfaces for the web.Full-stack engineering with a primary focus on designing scalable backend systems.Troubleshooting complex streaming challenges.Taking ownership of the complete development cycle of features from ideation to production.Writing code efficiently, shipping frequently, and making a substantial impact on our business by facilitating the scaling of our content.Your Profile5+ years of industry experience as a Backend Engineer, ideally within a fast-paced startup environment.Bonus: Experience on an app that has reached over 1 million users.Exceptional problem-solving and communication skills, along with the ability to work effectively in a collaborative environment.

About FieldguideAt Fieldguide, we are transforming the landscape of global commerce by revolutionizing the approaches to cybersecurity, privacy, and financial audits. Our innovative software solutions empower professionals to establish trust within businesses, enhancing their efficiency and delivering superior results.As a remote-first company based in San Francisco, CA, we are supported by prestigious investors such as Bessemer Venture Partners, 8VC, Y Combinator, and Floodgate. We pride ourselves on cultivating a diverse workforce and are committed to fostering an inclusive, humble, and high-performing company culture.About the RoleWe are seeking to onboard Software Engineers at various levels to contribute to our expanding team. Depending on your background and aspirations, you could work as a mid-level engineer, assume leadership responsibilities, or influence the technical direction across teams and systems. The specific level will be assessed during the interview process based on your experience and capabilities.This position offers a unique opportunity to make a significant impact in a company that has achieved product-market fit and is poised for substantial growth, challenging outdated audit and accounting tools that have long been overlooked.Your ResponsibilitiesCraft, develop, and implement high-quality features that create value for customers and drive business success.Work collaboratively with product and design teams to transform complex challenges into user-centered solutions.Maintain a balance between rapid iteration and sustainable system health.Continuously enhance our technology stack, developer workflows, and reliability standards.Foster a nurturing, growth-focused engineering culture based on trust, continuous learning, and excellence.

Join our dynamic team at Sonsoft, Inc. as a J2EE Developer where you will leverage your expertise in Core Java, Spring Boot, and MAVEN to create innovative software solutions. You will be responsible for developing and maintaining high-performance applications that meet the needs of our clients. Collaborate with cross-functional teams to design, implement, and optimize software applications.

Join Discord as a Software Engineer specializing in Safety Experience! In this role, you will be at the forefront of creating a safe and engaging environment for our users. You'll collaborate with cross-functional teams to design, develop, and implement robust safety features that enhance community interactions. If you're passionate about building innovative solutions and making a difference in user safety, we want to hear from you!

Join our dynamic team at Betasoft Systems as an Android Developer! We are seeking a talented individual who is passionate about mobile technology and eager to contribute to innovative projects. In this role, you will be responsible for designing and developing high-performance Android applications that enhance user experience and functionality.

Key Responsibilities * Actively engage in hands-on development * Architect and develop cutting-edge applications for the Android ecosystem * Prioritize the creation of secure and high-performance applications. * Collaborate with diverse teams to conceptualize, design, and implement innovative features * Integrate internal and external data sources and APIs * Conduct unit tests to ensure code robustness, covering edge cases, usability, and overall reliability * Address bugs and enhance application performanceEssential Qualifications* Bachelor's or Master's degree in Computer Science, Engineering, or a related field * 6+ years of dedicated experience in Android development. * Demonstrated software development expertise and strong Android skills * Proven track record of publishing at least one original Android application on the Google Play Store * Familiarity with popular Android libraries (such as Dagger, Retrofit) and application compatibility libraries (like Data Binding) for developing applications compatible with all Android devices. * Experience in invoking REST APIs and parsing JSON * Knowledge of mobile security, including encryption and API security. * Comprehensive understanding of the complete mobile development lifecycle

About SemgrepSemgrep is the vanguard of code security, revolutionizing the way developers create software by enabling frictionless innovation. Our platform aids teams in identifying, flagging, and resolving real security issues prior to deployment, supported by a security system that evolves with every line of code written. Semgrep ensures the integrity of code during development and provides essential guardrails, allowing developers to work swiftly and securely. Trusted by prominent organizations such as Snowflake, Dropbox, and Figma, Semgrep enhances visibility and control for security teams while delivering solutions seamlessly within the developer workflow. Our AI technology minimizes false positives and prioritizes actionable vulnerabilities, achieving validation from 95% of security experts across over 6 million findings.Founded in San Francisco and backed by leading venture capital firms like Menlo Ventures, Felicis Ventures, Lightspeed Venture Partners, Redpoint Ventures, and Sequoia Capital, Semgrep has been recognized by Gartner in Application Security Testing. Discover more at semgrep.dev.About the RoleThe Infrastructure team at Semgrep manages the critical cloud infrastructure that supports both internal and external applications, including our flagship offerings, Semgrep Code and Semgrep Supply Chain. Our mission is to empower Semgrep employees to confidently build, operate, and maintain their systems. We achieve this by offering a cohesive platform that transitions projects seamlessly from code to cloud, utilizing CI/CD systems, Kubernetes in AWS environments, and robust tools for production software operations.In this role, you will immerse yourself in the application security domain, collaborating with seasoned engineers to develop a robust infrastructure platform and build secure, reliable, and high-performing distributed systems. Embrace Semgrep’s transparent culture, where your insights and contributions can directly shape the success of our startup. Your work will play a vital role in positioning Semgrep as a leading static-analysis project, making a lasting impact not only within our organization but also in the broader developer community.Your Responsibilities:Collaborate with senior and staff engineers to design, implement, and deploy infrastructure initiatives.Learn and apply infrastructure best practices in conjunction with team members.Take ownership of projects, platforms, and tools within the team, managing them over several weeks.

We appreciate your interest in joining Uncountable Engineering!About UsAt Uncountable, we are on a mission to transform industrial research and development. We are looking for passionate and innovative platform engineers who are eager to enhance user experience and scale web applications effectively. Join us in building a cutting-edge development platform that will empower Fortune 500 companies.Role OverviewAs a Senior Full-Stack Engineer, you will play a pivotal role in developing the Uncountable Web Platform, a tool where scientists can upload and analyze their experiments. This position will involve an equal blend of front-end and back-end work, allowing you to take full ownership of the platform's development. You will also have the opportunity to engage directly with customers and lead enterprise software deployments.

ABOUT MITHRLAt Mithrl, we envision a future where innovative medicines are delivered to patients in mere months instead of years, and where scientific advancements occur at the speed of thought.We are pioneering the world's first commercially available AI Co-Scientist, a transformative discovery engine that rapidly converts complex biological data into actionable insights. Scientists can pose inquiries in natural language, and Mithrl provides comprehensive analyses, novel target suggestions, hypotheses, and patent-ready documentation.Our impressive growth reflects our success:Achieved 12X year-over-year revenue growthTrusted by leading biotech companies and major pharmaceutical firms across three continentsFacilitating significant breakthroughs from target discovery to patient outcomes.ROLE OVERVIEWWe are searching for a QA Engineer specializing in Scientific Software to develop the testing, validation, and monitoring infrastructure that ensures the accuracy and reliability of the Mithrl AI Co-Scientist. This position necessitates a PhD-level scientist or computational biologist who comprehends the intricacies of the drug development lifecycle and possesses practical experience with omics data. A solid scientific foundation is crucial for assessing the biological relevance of Mithrl's outputs.In this role, you will implement automated testing for analysis workflows, data ingestion pipelines, and discovery applications. You will establish CI systems for early regression detection, set up monitoring and alerting for system performance, and ensure every module in Mithrl generates scientifically valid and reproducible outputs. This position is a vital link between scientific knowledge and software quality engineering, essential for maintaining trust in Mithrl's analytical capabilities.If you are a scientist passionate about product reliability, reproducibility, and the validation of machine learning-powered scientific tools, this role offers a uniquely impactful opportunity.KEY RESPONSIBILITIESDevelop automated testing frameworks for data ingestion, analysis modules, discovery applications, and new product features.Create scientific validation frameworks to ensure correctness and reproducibility of machine learning-driven biological analyses.Implement continuous integration workflows that conduct end-to-end tests with every commit, identifying scientific and computational regressions.Establish monitoring and alerting systems to track health, performance, and reliability metrics.

Join the innovative team at fal and be a pivotal player in the GenAI media revolution! We are looking for skilled Backend Engineers who are passionate about leveraging their extensive experience with backend APIs and robust HTTP client/server design. In this role, you will develop high-performance, reliable proxies for our partner model providers.

About UsAt doss, we are pioneering the future of operational efficiency with our innovative platform, often referred to as the “Terraform for operators.” We are developing an AI-driven schema layer that powers a customizable data warehouse, enabling physical-goods companies to rapidly adapt their record systems in alignment with the evolving pace of their business operations.Imagine leveraging AI foundation models for seamless schema migrations, achieving real-time observability across operational and financial data, managing complex git versioning for schema and data changes, and creating workflows that are as flexible as infrastructure code.Your RoleCollaborate closely with design teams and fellow engineers to rapidly develop intuitive and lightning-fast web experiences.Play a crucial role in shaping the technical roadmap by prioritizing features that enhance customer-facing experiences.Develop adaptable infrastructure and components that can scale in a composable software environment, similar to tools like Retool, Airtable, Zapier, and Figma.Design a versatile entity-attribute-value (EAV) data model and schema-as-code platform that supports customer instances while ensuring transactional integrity.Your SkillsAbility to initiate and execute projects in ambiguous environments, transitioning from zero to one.Proficient in Typescript, React, NextJS, and Tailwind CSS.Familiarity with GraphQL, Postgres, ORMs, and Node (Express).Comfortable utilizing internal APIs to construct complex front-end interfaces and components.Knowledge of various databases including Postgres, Elasticsearch, DuckDB, and Memgraph.Who You AreTeam Player: You foster positivity, openness, and curiosity within the team.Growth Mindset: You view every challenge as an opportunity to learn and enhance yourself, your team, and the organization.Craftsmanship: You take pride in delivering high-quality work.Customer-Centric: You prioritize the customer experience and aim to create delightful products.Pragmatic: You make informed decisions based on circumstances rather than strict theories.Low Ego: You thrive in collaborative settings where team support is paramount.

Join Our Team as a Senior Fullstack Engineer!Location: Hybrid - San Francisco or Palo Alto Office, Tuesday/ThursdayYour Impact:We are on a mission to transform healthcare, and we’re seeking a talented Senior Fullstack Engineer to enhance our Patient Experience vertical. In this role, you will be instrumental in developing applications that streamline the patient journey from discovery to ongoing care management. You will lead significant projects through all phases of development, including brainstorming, architectural design, execution, testing, and iteration.If you are a motivated, solution-oriented engineer eager to make a difference in a purpose-driven environment, we want to hear from you!

At Composio, we are developing advanced infrastructure that enables agents to seamlessly interact with essential work tools such as GitHub, Gmail, Notion, Salesforce, and more. Our dedicated team of engineers is committed to tackling challenges ranging from contextual understanding to search functionalities, ensuring we provide an exceptional bridge between your agents and their tools.Having secured a $25M Series A funding from Lightspeed, alongside prominent angel investors like Guillermo Rauch (CEO of Vercel), Dharmesh Shah (CTO of HubSpot), and Gokul Rajaram, we have experienced remarkable growth, tripling our ARR at the start of this year. Our clientele includes notable names from Y Combinator cohorts to Wabi, Glean, Zoom, and beyond.Your RoleEnhance the experience of teams utilizing our platform by refining our core APIs and SDK.Create intuitive interfaces for both frontend and SDK applications.Take ownership of product development from concept through to production.Collaborate closely with customers to cultivate their loyalty while enhancing the product.Craft clear and concise documentation.