Backend Software Engineer - Ruby on Rails | San Francisco

Join Cardless as a Backend Software Engineer and become an integral part of our innovative team! In this role, you will design, develop, and enhance the robust systems that drive our co-branded credit card platform, covering key areas such as applications, accounts, transactions, fraud detection, risk management, and customer rewards.Your contributions will be essential in ensuring the scalability, security, and performance of our backend systems. You will engage in architectural planning and decisions to evolve our platform as we expand.

Cardless seeks a Data Analyst in San Francisco to help transform raw data into actionable insights. The work in this role shapes how teams refine internal processes and enhance the customer journey. Insights generated here play a direct part in guiding business decisions across the company. Key Responsibilities Analyze datasets to identify trends and patterns that influence business strategy Create clear, accessible visualizations to communicate findings to team members Apply statistical techniques to support recommendations and assist in decision-making Location This position is based in San Francisco.

As the Customer Support Lead at Cardless, you will be instrumental in leading our customer support team to deliver exceptional service and support to our valued customers. You will manage daily operations, ensuring that the team meets and exceeds performance targets while providing a positive customer experience. Your leadership will foster a culture of excellence and continuous improvement within the team.

Cardless creates credit card and loyalty platforms designed to help consumer businesses build stronger customer relationships. The company works with partners such as Coinbase, Bilt, and Qatar Airways, integrating credit card experiences directly into partner offerings. Headquartered in San Francisco, Cardless has raised about $150 million from investors including Spark Capital, American Express, and Activant Capital. The team values curiosity, humility, and a sense of ownership. Employees are encouraged to take responsibility for their work in an environment that balances speed with thoughtful decision-making. Role overview The Finance Operations Lead manages daily fund flows, prepares reports for lenders and partners, and oversees the borrowing base process for Cardless and its brand partners. This is a hands-on, individual contributor position that emphasizes accuracy and timely execution. Sitting at the intersection of Finance, Capital Markets, Data, and Operations, this role ensures compliance with credit facility requirements and supports effective liquidity management. What you will do Oversee daily operations related to fund flows Prepare and deliver reports for lenders and partners Manage the borrowing base process across Cardless and partner programs Maintain accuracy and integrity in all funding flows and reporting Collaborate with teams in Finance, Capital Markets, Data, and Operations Focus on automation, controls, and building scalable processes Support compliance with all relevant credit facility requirements Who thrives here People who are meticulous and disciplined in their work Those comfortable handling high-volume, transaction-focused tasks Individuals skilled in modern data and banking platforms Professionals who prioritize process automation and strong controls Location This position is based in San Francisco.

Cardless creates digital-first credit card products for well-known brands. The company has earned recognition, including a spot on the Forbes Fintech 50 in 2026, by focusing on integrated and customer-friendly financial solutions. Role overview This Corporate Counsel position is based in San Francisco and reports directly to the General Counsel. The attorney in this role will support Cardless’s commercial and capital markets operations, providing legal guidance across a variety of commercial and financing transactions. What you will do Advise on commercial agreements and transactions involving capital markets Develop and refine legal processes to help the legal function scale and adapt as the company grows Work closely with business teams and executive leadership on legal matters Assist with the adoption and use of AI tools to make legal workflows more efficient Requirements Licensed attorney with a detail-oriented and proactive approach Comfortable navigating a high-growth, evolving company environment Interest in technology and legal solutions that use AI Experience handling commercial and capital markets legal work

Join 10alabs as a Backend Software Engineer where you will play a vital role in designing and developing robust backend systems. You will work closely with cross-functional teams to create scalable and efficient software solutions that meet the needs of our clients. If you are passionate about technology and eager to tackle complex challenges, we want to hear from you!

Role OverviewLocated in the heart of San Francisco, CA, this position is integral to our headquarters and does not support full-time remote work.Compensation for this role ranges from $150,000 to $250,000 annually, depending on experience, along with equity and comprehensive benefits.About FurtherAIAt FurtherAI, we are pioneering advanced AI agents tailored for the insurance sector, a market primed for innovation worth trillions. Having successfully secured over $30 million from prestigious investors such as Andreessen Horowitz, Y Combinator, Nexus, South Park Commons, and Converge, we've experienced a remarkable tenfold revenue growth this year. Our clientele includes some of the most renowned names in insurance, including a top 5 global insurance company. Our team merges profound AI knowledge with extensive entrepreneurial experience.We are currently seeking an extraordinary Software Engineer to join our foundational team and help shape our product and organizational culture.Why Work With Us?Accelerated Growth: Experience rapid revenue growth post-product-market fit.Exceptional Team: Our founding group features talents from Apple AI Research, four ex-Y Combinator founders, and six successful entrepreneurs. Our engineering team boasts backgrounds from Apple, Microsoft, Google, and Amazon.Deep Technical Challenges: Collaborate with a staff research scientist and a team of seven engineers tackling advanced AI and scalable backend solutions.Significant Market Influence: Our work is transformative, reshaping the insurance industry's operational landscape.Entrepreneurial Spirit: Ideal for those looking to take ownership of critical product areas and possibly launch their own ventures in the future.Your ResponsibilitiesDevelop and enhance the core product, ensuring optimal performance, reliability, and ongoing improvements.Take charge of substantial elements of the backend architecture using Python.Work closely with founders to define and guide the technical roadmap.Embrace a culture of extreme ownership within a dynamic, high-performance environment.Engage in-person at our San Francisco office (5 days a week).

About HappyRobotHappyRobot is a pioneering AI-native operating system designed for the real economy. We bridge the gap between intelligence and action by integrating real-time insights, specialized AI operatives, and orchestrating intelligence. Our technology empowers enterprises to manage complex, mission-critical operations with genuine autonomy.Our AI OS continually enhances knowledge, optimizes processes, and adapts over time. We are focusing initially on supply chain and large-scale industrial operations, where resilience, speed, and ongoing improvement are crucial—allowing humans to concentrate on strategy, creativity, and other high-value activities.Discover more about our vision in our Manifesto. To date, HappyRobot has secured $62M in funding, including a recent $44M Series B round in September 2025. Our investors include Y Combinator (YC), Andreessen Horowitz (a16z), and Base10—partners who share our commitment to transforming enterprise operations. We are channeling this investment into building a world-class team—individuals with relentless drive, exceptional problem-solving abilities, and a passion for pushing boundaries in a dynamic, high-intensity setting. If this resonates with you, consider joining HappyRobot.About The RoleAt HappyRobot, Backend Software Engineers take ownership of critical components of our product and infrastructure from inception to deployment. We are seeking passionate builders who excel in uncertain environments, value craftsmanship, and desire true ownership of their creations.

Join Our Innovative Team at ClericAt Cleric, we are on a mission to develop a cutting-edge autonomous AI agent designed to investigate and resolve production incidents efficiently. Our state-of-the-art agent utilizes large language models (LLMs) alongside advanced tools to comprehend complex systems, analyze problems, and implement corrective measures, even for unprecedented issues.Our technology is already making waves in high-scale companies across various sectors, including fintech, ride-sharing, and autonomous vehicles.About the RoleWe are seeking a talented Backend Software Engineer to join our dynamic team in scaling our autonomous agent technology. This position is perfect for engineers eager to develop, deploy, and enhance AI systems within real-world environments.You will collaborate closely with senior engineers on agent reasoning, integrations, and runtime systems, playing a pivotal role in delivering impactful customer-facing features.Your ResponsibilitiesEnhance capabilities of our autonomous agent and streamline tool execution workflowsDevelop and expand integrations with existing production systemsAssist in creating tools for agent evaluation and observabilityPartner with senior engineers to design, implement, and deliver new featuresGain insights into building reliable AI systems for production environmentsQualifications1–2 years of professional experience in software engineeringStrong understanding of software engineering principles and system designProficiency in Python (familiarity with other programming languages is a plus)A keen interest in AI, machine learning, and agentic systemsA passion for rapid learning and tackling real-world production challengesPreferred SkillsFamiliarity with AI/ML systems or LLM-based productsExperience with distributed systems or cloud infrastructureBackground in startup or fast-paced team settingsOur Work CultureSmall teams that create a significant impactEncouragement of radical candor in a supportive environmentEmphasis on in-person collaborationAn AI-first approach in all our endeavors

About braintrustBraintrust is at the forefront of AI observability, merging evaluation and observability into a seamless workflow. Our platform empowers developers to gain critical insights into AI behavior in production environments and provides tools for optimization.Renowned companies such as Notion, Stripe, Zapier, Vercel, and Ramp leverage Braintrust to assess models, test prompts, and identify regressions, transforming production data into enhanced AI performance with each update.About the RoleWe are seeking a passionate Backend Engineer to contribute to the foundational infrastructure of innovative AI development tools.Braintrust operates as a real-time, highly available data platform within both SaaS and self-hosted ecosystems. Your contributions will be pivotal in scaling our data ingestion pipelines, enhancing our open-source libraries, and ensuring optimal system performance and reliability. If you excel in a dynamic environment and relish tackling complex systems challenges with a product-oriented mindset, we would love to collaborate with you.Your ResponsibilitiesAs a Backend Engineer at Braintrust, you will play a key role in shaping the core platform that facilitates LLM-native development:Design and deploy features that provide users with profound insights into their LLM utilization and performance metrics.Integrate, proxy, cache, and aggregate data from leading model providers such as OpenAI, Anthropic, and Gemini, which our clients depend on.Create and refine robust, efficient open-source libraries for tracing and evaluating LLM calls within client applications. Explore our SDKsDevelop highly available real-time data pipelines to ingest, store, and query extensive volumes of structured and semi-structured AI usage data.You will also collaborate closely with product engineers to deliver polished, comprehensive features that address real customer challenges, including:Bundling and uploading JavaScript and Python code snippets for on-demand function calls in LLM workflows.Facilitating the parsing and uploading of attachments from LLM multimodal outputs for long-term storage.Implementing role-based access controls and data retention protocols for enterprise scenarios.

Astranis is revolutionizing space communications by constructing advanced satellites for high orbits, enabling humanity to expand its reach into the solar system. Our satellites currently deliver dedicated, secure networks to a diverse range of sophisticated clients globally, including large corporations, government entities, and the US military. With five satellites successfully in orbit and many additional launches on the horizon, we are addressing a robust backlog of over $1 billion in commercial contracts.As the preferred satellite communications partner for customers with stringent uptime, data security, network visibility, and customization requirements, Astranis has successfully secured over $750 million in funding from top investors, including Andreessen Horowitz, Blackrock, and Fidelity. Our team of 450 engineers and entrepreneurs works out of our impressive 153,000 sq. ft. headquarters in Northern California, USA, where we design, build, and operate our satellites.Backend Software EngineerBefore a satellite can be launched into orbit, it undergoes a comprehensive process that includes financing, procurement, manufacturing, and testing. As a Backend Software Engineer, you will play a pivotal role in constructing the software systems that facilitate spacecraft development, testing, and manufacturing, ensuring seamless integration with our supply chain. This high-impact role encompasses multiple domains—from procurement and manufacturing to cloud services and data pipelines—contributing significantly to efficient engineering workflows, business intelligence, and scalable flight operations.In this role, you will collaborate closely with cross-functional teams, including hardware engineers, manufacturing specialists, operations personnel, and satellite flight control teams, to develop internal tools that streamline processes and accelerate development. You will be responsible for owning and delivering scalable systems that enable us to efficiently build, test, and launch satellites.This position supports both commercial and US Government satellite programs.

Why Choose Doppel?At Doppel, we are at the forefront of combating one of the most significant challenges posed by artificial intelligence: the prevalence of sophisticated social engineering tactics. With an alarming rise in scams, deepfakes, and other malicious attacks across various digital platforms—including websites, social media, advertisements, and encrypted messaging apps—our mission is both ambitious and vital: to create a safer internet by outsmarting these rapidly evolving digital threats.Supported by leading investors like a16z and Bessemer, and trusted by globally recognized brands such as OpenAI, United Airlines, and Coinbase, Doppel is expanding rapidly. If you are passionate about leveraging bold technology to tackle real-world challenges, we want to connect with you.Our VisionWe are developing an AI-native platform dedicated to defending against social engineering attacks.This entails creating scalable systems that continuously monitor billions of domains, social media accounts, applications, dark web forums, and more, utilizing AI agents to detect and neutralize digital threats effectively.Your RoleWe are seeking a seasoned backend engineer to design and enhance an automated system aimed at streamlining various Security Analyst functions. Our objective is to verify and neutralize threats within minutes through AI-driven automation. Recent achievements include:Developed a sophisticated LLM engine that quadrupled verification efficiency for our highest volume product line, enabling rapid takedowns at scale.Created a QA and data labeling tool to facilitate a seamless feedback loop among human analysts, machine learning models, and LLM agents.As a member of our San Francisco team (in-office a minimum of three days a week), you will:Play a vital role in developing systems that safeguard billions from AI-generated scams and digital threats.Take ownership of projects from gathering product requirements to continuously evaluating and refining released features.Mentor junior engineers, nurture a high-performance team culture, and contribute to shaping the team’s roadmap.Participate in monthly team dinners, happy hours, and social events (including outings to the Exploratorium, Valkyries games, etc.).What We Provide A mission-driven culture characterized by humility, high accountability, deep customer focus, and an abundance of exceptional talent. Complimentary lunch and dinner provided in the office. Flexible Paid Time Off (PTO).

About CollateCollate is a cutting-edge AI-driven document generation platform specifically designed for the life sciences sector. Our innovative technology automates the paperwork process, enabling our clients to deliver life-saving medical innovations to patients significantly faster. As a comprehensive solution, Collate supports every phase of development for drugs, diagnostics, and medical devices—from initial concept to market launch.Our visionary CEO Surbhi Sarna, a former General Partner at Y Combinator, founded nVision Medical, which pioneered a novel method for detecting ovarian cancer before its acquisition by Boston Scientific. Our CTO Nate Smith, previously a Visiting Partner at Y Combinator and founder of Lever, leads our talented team of AI researchers, engineers, and designers who have backgrounds at industry giants such as Google, Nvidia, Meta, Netflix, Amazon, Airbnb, Hippocratic AI, and Grail. Notably, 40% of our team members are former startup founders themselves.As a compact yet highly skilled team, we have secured over $30M in seed funding from top-tier investors including Redpoint, First Round Capital, Conviction, and Y Combinator, as well as healthcare and AI leaders. This is a unique opportunity to join a company at the forefront of transformative change, guided by experienced founders with the resources to scale effectively.About the RoleWe are seeking a talented Backend Engineer who will play a crucial role in designing and scaling the systems that underpin Collate’s offerings. You will be responsible for developing APIs, services, and the infrastructure that form the backbone of our platform, ensuring they are efficient, dependable, and secure as we transition from prototypes to large-scale implementation.This position is perfect for individuals who thrive on tackling complex system challenges, flourish in an early-stage setting, and wish to see their contributions directly impact advancements in the life sciences field.Modern Tech StackCollate employs a contemporary tech stack aimed at delivering a highly reliable and available platform. Our backend services are built using Go, while we utilize Postgres as our primary database. Frontend development is powered by TypeScript and React, and Python is utilized for AI and machine learning services. Our infrastructure is hosted on AWS, employing Kubernetes for orchestration along with Terraform and Argo CD for configuration management.

Founded in the heart of Silicon Valley in 2009 by visionary entrepreneurs Marc Andreessen and Ben Horowitz, Andreessen Horowitz, commonly referred to as a16z, is a prominent venture capital firm committed to supporting audacious entrepreneurs who are shaping the future through technology. We are stage agnostic, investing across various stages from seed to venture and growth-stage technology companies. Our diverse portfolio spans industries including AI, bio + healthcare, consumer, crypto, enterprise, fintech, games, and initiatives promoting American dynamism. With $90 billion under management across multiple funds, we are at the forefront of innovation and investment.Our team is characterized by a profound respect for entrepreneurs and the intricate process of building companies. We have proudly invested in groundbreaking companies such as Anduril, Airbnb, Coinbase, Cursor, Databricks, Deel, Figma, GitHub, Roblox, SpaceX, and Stripe. We are dedicated to empowering founders and their teams to create significant impacts in the world.

Join Layerfi as a Backend EngineerAt Layerfi, we are revolutionizing the accounting landscape for small and medium-sized businesses (SMBs). With a decade of experience, we’ve established a powerful ecosystem of software tools that facilitate various business operations. However, the accounting sector has fallen behind, leaving SMBs to struggle with disjointed software and costly bookkeeping services.We are creating a cutting-edge accounting software that seamlessly integrates with the existing tools that SMBs rely on daily. Our platform empowers software companies to deliver modern accounting solutions and bookkeeping services to their clients, eliminating the need for outdated tools and expensive bookkeepers.Your RoleWe seek engineers who aspire to build not just products but also a strong team and company. This requires a blend of technical expertise across our tech stack along with unique skills such as:Forward-thinking coupled with a deep understanding of customer needs.A keen curiosity about technical and business challenges.Ability to navigate competing priorities while aligning with company objectives.A strong sense of ownership in product and team decisions.A passion for collaboration and enhancing the strengths of your colleagues.Our ideal candidates typically possess:A minimum of 2 years of experience in robust software development teams.Experience navigating the highs and lows of product development from inception to launch.A proven track record in team leadership and growth.We value proactive individuals who are eager to tackle challenges and seize opportunities, and we welcome those who reach out even if they don’t precisely meet the criteria.Our Technology StackWe do not focus on how familiar candidates are with our specific tech stack. One of the advantages of hiring exceptional engineers is our confidence in their ability to adapt and learn quickly, with support from the team. However, we do want all candidates to feel excited about the tools and environment they will engage with from day one.API language: KotlinEmbedded components: ...

At Anara, we're seeking a skilled Backend Software Engineer to join our dynamic team in San Francisco. As a key contributor, you will develop the robust infrastructure that powers our AI-driven research tools. Your expertise will help us handle the challenges of processing millions of files and scaling our services for hundreds of thousands of users.Key Responsibilities:Design and implement scalable backend systems for AI-enhanced research applications.Work collaboratively with the engineering team to optimize our retrieval pipeline, focusing on improving response quality, speed, and reliability.Establish and promote best practices for model deployment and prompt engineering.Analyze and enhance system performance while balancing cost efficiency to ensure rapid growth.Lead the design and automation of evaluation pipelines to continuously assess and improve the reliability of our AI agents.

Join demo.levels.fyi, a trailblazing software company that empowers real-time collaboration on vital workflows. Established in 2012, we proudly serve over 10,000 clients globally and are backed by esteemed investors, including Example Capital. Having successfully raised our Series C, demo.levels.fyi is currently valued at $750 million.As a Backend Engineer, you will be an integral part of our dynamic team, directly reporting to the team manager. This pivotal role will enable you to influence various workflows and contribute to our innovative projects.

About HappyRobotHappyRobot is revolutionizing the real economy with our AI-native operating system designed to bridge the gap between intelligence and action. By integrating real-time insights with specialized AI capabilities, we empower enterprises to manage complex operations autonomously.Our AI OS continuously accumulates knowledge, optimizes various processes, and adapts over time. We are initially focusing on supply chain and large-scale industrial operations, where speed, resilience, and ongoing improvement are paramount—allowing human resources to concentrate on strategic and creative high-value tasks.Discover more about our vision in our Manifesto. So far, HappyRobot has successfully raised $62M in funding, including a recent $44M in Series B financing as of September 2025. Our esteemed investors include Y Combinator (YC), Andreessen Horowitz (a16z), and Base10, who share our mission to transform enterprise operations. We are leveraging this investment to build a top-tier team of individuals with unwavering motivation, exceptional problem-solving capabilities, and a drive to exceed limits in a dynamic working environment. If this resonates with you, we want you at HappyRobot.About The RoleAt HappyRobot, our Senior Backend Software Engineers are entrusted with significant components of our product and infrastructure, overseeing projects from inception to deployment. We are seeking passionate builders who thrive in uncertain environments, value craftsmanship, and desire genuine ownership of their creations.

Join our dynamic team at unify as a Senior Backend Software Engineer, where you will leverage your expertise to design and implement robust backend systems that enhance our product's performance and scalability. You will collaborate closely with cross-functional teams to develop innovative solutions that meet our customers' needs.