Top Principal Software Engineer Jobs in San Francisco, CA

Set technical direction org-wide, own highest-stakes architectural bets, lead the AI/agents rebuild, raise engineering standards, mentor senior engineers, and align teams with product and platform strategy.

The Principal Software Engineer will design and implement systems for the advertiser experiences at Snap, lead technical vision, mentor engineers, and innovate on creator marketplace products.

Lead technical ownership of a global platform for safe change: distributed key-value storage, progressive configuration delivery, testing and health-mediation. Write production code, design systems, review senior proposals, integrate LLMs, and drive cross-team initiatives to improve reliability, rollout safety, and developer productivity.

The Principal Software Engineer will design automated ad serving systems, lead technical direction, collaborate with teams, and mentor engineers.

As a Senior Principal Engineer, you'll define and drive the technical strategy for customer experience platforms, lead architectural decisions, and mentor engineering teams to enhance customer and agent experiences.

Lead design, build, deployment, and operation of highly resilient, high-throughput configuration and publishing systems. Define long-term architecture and strategy, mentor senior engineers, diagnose and fix performance bottlenecks, and leverage AI tools to improve engineering productivity and platform capabilities.

Lead design and build of scalable backend systems and data platforms; own architecture and production deployments; improve reliability, performance, and observability; mentor engineers and collaborate with Product, Data Science, SRE, and Security.

Lead architecture and technical direction for an AI-first SaaS product (Growth Studio). Define scalable services, APIs, data flows, and AI-enabled workflows; guide integrations, run architecture/code reviews and POCs; mentor engineers; produce technical documentation; and partner with product, UX, QA, and ops to deliver reliable, secure, and maintainable platform capabilities for GovCon customers.

This role involves leading technical projects across multiple teams, designing scalable systems, collaborating with cross-functional teams, and mentoring engineers, focusing on payroll and tax systems at Gusto.

Lead long-term technical strategy and execution across multiple teams, architecting and evolving foundational frontend/backend systems and platforms at massive scale. Drive AI/ML adoption, solve ambiguous, high-impact problems, remain hands-on in critical system design and implementation, and align senior leaders on roadmaps and engineering standards.

Lead architectural evolution of a high-traffic B2B SaaS supplier platform: define microservice boundaries, APIs, CI/CD, multi-cloud deployment, security, multi-tenancy, and mentor engineers while partnering with SRE, product, and business teams.

Lead architecture, design, and delivery of PET product features; write production full‑stack code; champion testing, observability, CI/CD and operational readiness; mentor engineers and collaborate with product to shape technical roadmap.

Lead development of core client systems and engine-level infrastructure in Unity/C#. Diagnose and fix cross-cutting performance issues, upgrade third-party SDKs, evolve build tooling, produce design docs, scope multi-week infrastructure initiatives, mentor engineers, and drive profiling, optimization, and architecture changes to enable future features.

Design and implement high-performance backend systems in Rust, optimize architectures, participate across the development lifecycle (debugging, testing, optimization), integrate third-party devices and data, incorporate AI tools, mentor senior engineers, and lead architectural and technical strategy across teams.

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 design and delivery of a unified observability platform: architect data ingestion, query performance, and telemetry integration. Mentor engineers, drive cross-team alignment, use AI-assisted development, and own production operation and customer outcomes.

Build autonomous accounting agents and a ledger, integrate financial data providers, and ship daily product features using TypeScript/Next.js. Move quickly, make decisions, and iterate based on customer problems in a high-urgency, in-person startup.

Lead architecture, implementation, and delivery of R&D platform infrastructure (cloud, Kubernetes, IaC). Provide technical leadership and mentorship, build AI-native developer tooling, partner with scientists to translate needs into production-grade platform capabilities.

Join a talent network connecting principal front-end, back-end, and full-stack engineers with VC-backed startups. Responsibilities include driving technical architecture, building scalable full-stack applications, designing APIs and cloud-native services, optimizing performance and reliability, leading deployment and CI/CD best practices, and mentoring senior engineers while aligning technical decisions with product and business goals.

Design and maintain Salesforce Workspaces devcontainer images and features, optimize Bazel build infrastructure and RBE, implement control plane services (Temporal, DynamoDB), ensure image supply-chain security, build observability/AI diagnostics, support incidents, and lead cross-team platform initiatives to improve developer productivity and reliability.

Design and build large-scale, highly available Responsible AI cloud services. Lead architecture, development, release, and production readiness. Collaborate with engineers, scientists, and product managers to integrate Responsible AI features across Azure AI and related services, drive DevOps practices, and improve performance, observability, and reliability.

Architect and build TeraWave Point of Presence infrastructure, implement and optimize wire-speed dataplane using DPDK/VPP, tune IP networking stacks (BGP/OSPF), drive performance engineering at the software-hardware interface, mentor engineers, and integrate PoP systems with the broader satellite communications ecosystem.

The Principal Software Engineer will define architecture for high-performance infrastructure, optimize RL environments, and turn prototypes into scalable systems, while resolving technical challenges.

Lead development of Codex Cyber's AI-driven security products: define technical roadmap, partner with trusted defenders and cross-functional teams, shape model training and access, build evaluation and safeguard systems, measure and mitigate misuse risk, and translate research into production tools and infrastructure.

Lead backend architecture and deliver reusable solutions, unblock engineering teams across the development lifecycle, drive complex design and bug fixes, set code review standards, mentor engineers, collaborate on company-wide projects, and make technical decisions balancing correctness, performance, and customer impact.