Zach Sierakowski

Scaling GitHub for AI | Staff Engineer

United States

About

Staff Software Engineer with 10+ years building large-scale distributed systems and developer platforms used by millions of users. Proven track record re-architecting monolithic systems into high-performance Go services, improving reliability, cost efficiency, and global scalability. Experienced in leading cross-team platform initiatives and shaping identity, authentication, and access systems, while designing scalable, secure, and reliable systems that enable teams and improve developer experience.

Experience

  • GitHub (Full-time · 6 yrs)
    • Staff Software Engineer, Platform & Identity
      Jul 2025 - Present · 1 yr

    • Senior Software Engineer, Identity
      Jul 2021 - Jun 2025 · 4 yrs

    • Software Engineer III, Identity
      Jul 2020 - Jun 2021 · 1 yr

      • Own the architecture and evolution of GitHub’s authentication platform in Go, delivering sub-10ms token validation for all authenticated API traffic while ensuring global-scale security, scalability, and reliability. • Redesigned GitHub’s conditional access system by decomposing monolithic ABAC logic into a dedicated Go service, enabling 500K+ RPS while reducing compute costs. • Mentored engineers and drove cross-team architectural initiatives, standardizing authentication and service access across GitHub’s backend platform. • Led the end-to-end design and launch of GitHub Mobile 2FA, scaling to 10M+ users and 5M+ authentications/month while strengthening platform security. • Designed edge-ready identity systems using CDC-based replication and optimized data access patterns to reduce backend load and improve global latency. • Drove platform-wide 2FA enforcement, increasing adoption by 54%, and established reusable patterns for service decomposition adopted across multiple teams. • Led the design and rollout of a self-serve enterprise provisioning system enabling sales-led onboarding without engineering involvement, reducing friction and improving time-to-value. • Prevented SMS abuse through rate limiting and CAPTCHA protections, reducing an estimated $700K in potential toll fraud.

  • Freelance Software Engineer, Consulting (Part-time) at Ox
    Jun 2021 - Dec 2023 · 2 yrs 7 mos

    • Partnered with the founder of an AI startup to build full-stack features, owning APIs, infrastructure, and frontend systems to rapidly ship AI-driven workflows from concept to production.

  • Software Engineer II, Core Services at Microsoft
    Aug 2019 - Jul 2020 · 1 yr

    • Delivered a developer-facing API token platform used across App Center integrations, enabling secure programmatic access for external developers and services. • Led recovery and completion of a stalled multi-version ORM upgrade, resolving a critical security vulnerability while improving reliability and maintainability of the data layer.

  • Software Engineer, Full Stack at Visionist, Inc.
    May 2016 - Aug 2019 · 3 yrs 4 mos

    • Built a real-time data platform using Kafka Streams and geospatial visualization, enabling large-scale event processing and analysis. • Designed autoscaling Kubernetes infrastructure and internal developer tooling, improving deployment workflows and frontend consistency across teams.

  • Freelance Software Engineer, Full Stack at Freelance
    May 2016 - May 2016 · 1 mo

    Freelancing since 2016, building websites and full-stack applications for clients acquired through referrals and Upwork. Consistently delivering successful projects on milestone-driven schedules.