Top Principal Software Engineer Jobs in San Francisco, CA

Lead the architecture, technical strategy, and roadmap for Microsoft's Windows ML compiler stack. Design high-performance compiler infrastructure, execution engines, optimization frameworks, and developer tools supporting CPU, GPU, and NPU workloads. Drive NPU enablement, graph optimization, scheduling, memory management, code generation, and hardware abstraction. Partner with silicon vendors and internal teams, influence AI hardware and platform strategy, lead cross-team initiatives, and mentor engineers developing on-device and generative AI capabilities.

Architect and develop foundational edge-computing runtime and integration platforms for connected-home devices. Build software models for device, spatial, and occupancy data; prototype and productionize new concepts; evaluate architectures; and provide technical leadership through design reviews, coding standards, mentoring, and cross-functional collaboration. The role spans edge computing, IoT, distributed systems, embedded environments, intelligent agents, networking, and secure systems within an exploratory R&D organization.

Lead technical architect and hands-on principal engineer for the SOC Experience team, building scalable investigation workflows, agentic LLM features, automation, remediation actions, and analyst tooling. Drive architecture, mentor engineers, prototype solutions, ensure reliability and observability, and partner with product, UX, and SOC stakeholders to turn operational problems into auditable, production-grade systems.

Lead legacy application assessments and modernization strategy for U.S. Air Force systems. Own architectural decisions, technical direction, and test strategy while collaborating with government engineers, vendors, product managers, researchers, and designers. Promote secure, compliant, agile engineering practices; coach government teams; evaluate technical environments; communicate recommendations; and demonstrate modern AI-assisted development practices. The role is fully remote, requires U.S. citizenship and CAC eligibility, and involves occasional quarterly travel to Air Force bases.

Lead end-to-end design and delivery of AI-infused, enterprise full-stack applications on Azure. Architect resilient solutions, build Copilot/agentic features, enforce engineering best practices, mentor engineers, collaborate with PM/UX teams, ensure quality/reliability, and support production services and integrations.

Lead autonomy-wide initiatives to achieve driverless freeway operation. Define technical vision, strategy, and roadmap; identify and close gaps to driver-out readiness; develop and validate freeway-driving algorithms; communicate risks and trade-offs to technical and executive stakeholders; and mentor engineers. The role requires significant experience taking autonomous vehicle freeway programs from supervised to driverless operation, plus deep expertise in an autonomy domain such as planning, perception, prediction, simulation, or systems engineering.

Principal Software Engineer responsible for the architecture, development, and technical direction of macOS and Linux endpoint agents. The role involves application-control enforcement, privileged services, OS event monitoring, secure communications, lifecycle management, installation and updates, debugging, code reviews, testing, observability, and mentoring. The engineer will collaborate across product, QA, security, support, and cloud teams while resolving complex systems, performance, reliability, and security issues.

Leads development of distributed AI infrastructure for large-scale reinforcement learning and LLM post-training. Designs scalable, resilient systems; optimizes model, hardware, and inference performance; improves developer tooling and engineering practices; mentors engineers; and supports production services through reliability engineering, incident response, telemetry, and on-call operations.

The role involves leading security initiatives, building security tools, conducting vulnerability assessments, and collaborating with teams to enhance cloud security and risk management.

Founding engineer responsible for architecting and building core product systems, writing scalable Python backend code, designing and maintaining AI/ML infrastructure, instituting best development practices (testing, CI/CD), collaborating on product roadmap, and mentoring future engineers.

Own cross-team, platform-level engineering initiatives end-to-end: architecture, migrations, observability, on-call, and customer outcomes. Drive AI-native tooling and agentic AI adoption, mentor senior engineers, and set technical standards across teams.

Lead the architecture and evolution of managed Kubernetes and cloud-native services. Provide cross-team technical oversight, standardize platform practices, integrate open-source technologies, improve scale, performance, security, and operational efficiency, and mentor engineering teams. The role requires expertise in Kubernetes-based platforms, container runtimes, cloud-native architectures, and Go, Python, or Bash.

Lead design and prototyping of generative AI experiences for autonomy development; drive UX for Hivemind products; perform user research, collaborate with CTO and product leads, and deliver reference implementations and integrations across full-stack web and edge systems.

Founding engineer responsible for architecting and building core product components, writing scalable Python code, designing and maintaining AI/ML infrastructure, implementing testing and CI/CD best practices, shipping backend production systems, collaborating on product roadmap, and mentoring future engineers.

Build and maintain parsing infrastructure, SDKs, data models, and services for hardware design collaboration. Develop parsers for circuit-design formats, binary file-merging capabilities, test harnesses, developer tooling, and performance improvements. Collaborate with engineering, product, sales, and other stakeholders to define interfaces, requirements, timelines, and constraints while driving autonomous, cross-functional projects.

Lead design, development, and delivery of mission-critical SIEM platform features. Define technical vision, own quality and uptime, mentor engineers, collaborate cross-functionally, build AI-assisted workflows, and drive performance, monitoring, and architecture decisions.

Design, implement, and ensure quality of systems stack, tools, and SDK integration for AI frameworks. Collaborate with hardware and ML teams, apply engineering principles, write low-level/high-performance code, define architecture, estimate scope, and drive coding standards.

Lead technical vision and architecture for AI frameworks, performance, benchmarking, and tooling. Drive cross-team alignment, mentor engineers, ship high-performance distributed software, and improve model onboarding, runtime performance, reliability, and Azure hardware efficiency.

Design and build distributed systems, high-performance APIs, real-time data pipelines, and intelligent LLM-powered applications processing billions of events daily. Develop advertising, identity, and intent platform capabilities using streaming, batch, and large-scale data technologies. Own system quality, scalability, performance, and observability while collaborating with product managers, data scientists, and engineers. Provide technical leadership and mentorship across initiatives involving ad infrastructure, identity resolution, behavioral analytics, and applied AI.

Work on end-to-end AI performance for LLMs: benchmark and optimize inference on GPUs and Microsoft silicon, build tooling for performance insights and model porting, implement and test components in AI/DNN frameworks, and collaborate with internal and external partners to reduce hardware footprint and accelerate deployments.

As a Senior Principal Software Engineer, you'll develop a unified data platform, architect infrastructure, implement APIs, and mentor teams, focusing on data processing and reliability.

Design and build high-performance UI and APIs, manage database architecture, optimize systems for reliability and performance, and collaborate cross-functionally in a scientific context.

Lead design and implementation of Replit's money infrastructure, focusing on pricing, billing, payments, and monetization while ensuring reliability and user-friendly experiences.

Build production-ready AI applications, services, APIs, reusable frameworks, and autonomous agents for enterprise quality engineering. Lead architecture and complex technical initiatives, integrate AI into software development and testing workflows, evaluate emerging technologies, and establish AI governance, security, observability, and development best practices. Partner across engineering, product, security, architecture, and data teams while mentoring engineers and shaping long-term AI strategy.

Lead the architecture and modernization of a complex enterprise SaaS platform while remaining hands-on with critical software design and development. Define technical direction, improve scalability, reliability, security, performance, and maintainability, and guide design and code reviews. Partner across engineering and product teams, resolve complex technical challenges, establish engineering standards, mentor engineers, and translate architectural strategy into practical delivery.