Job Opportunity: Principal Software Engineer at Microsoft 365 Copilot
Microsoft 365 Copilot is revolutionizing productivity by merging large language models with user data, Microsoft Graph, and the web. At the heart of this innovation is the Substrate Intelligence Platform (DSX) team, which powers personalized, secure, and scalable Copilot experiences across Microsoft 365—Teams, Word, Excel, PowerPoint, OneNote, and more.
Our team is at the forefront of constructing the infrastructure for tenant-isolated fine-tuning, a foundational platform capability that allows customers to personalize Copilot agents securely using their own data. This includes support for leading OpenAI models (e.g., GPT-5, O4 Mini) and open-source models such as Qwen, Mistral, and GPT-OSS.
We oversee the end-to-end fine-tuning platform via Heron, which encompasses:
- Data extraction and isolation
- Secure training and evaluation workflows
- Model deployment, migration, and lifecycle management
Our systems operate at an immense scale in multi-tenant environments, enforce strict security and compliance boundaries, manage shared GPU resources efficiently, and facilitate seamless onboarding of new models and customers.
Your Role
As a Principal Software Engineer, you will play a pivotal technical leadership role in shaping the next generation of Copilot’s fine-tuning and evaluation infrastructure.
This role goes beyond feature development. You will:
- Set the technical direction for core platform components
- Influence architecture and design decisions across multiple teams
- Tackle ambiguous, high-impact problems at the intersection of AI infrastructure, security, scale, and reliability
- Enable Copilot scenarios that unlock new customer value and revenue
You will collaborate deeply with partner teams across Azure Machine Learning, Foundry, Singularity, TCaaS (Tenant Copilot as a Service), Heron Infra, Copilot Inferencing, and Security & Compliance, driving alignment on data movement, isolation models, quota management, GPU fungibility, and model deployment strategies.
About Microsoft
Microsoft’s mission is to empower every person and organization on the planet to achieve more. Together, we embrace a growth mindset, innovate to empower others, and collaborate to realize our shared goals. Each day, we build on our values of respect, integrity, and accountability to foster a culture of inclusion where everyone can thrive.
Responsibilities
- Architect and lead the design of large-scale, distributed services that power tenant-isolated fine-tuning and evaluation workflows.
- Drive end-to-end technical ownership of critical platform areas, from data ingestion and training orchestration to deployment, rollback, and monitoring.
- Define and evolve secure data movement patterns across tenant boundaries, ensuring compliance with Microsoft security, privacy, and governance requirements.
- Establish long-term technical vision and roadmap for the Heron fine-tuning platform, balancing scalability, reliability, cost, and developer velocity.
- Lead cross-team technical reviews, influencing designs and fostering alignment across multiple organizations.
- Build frameworks and abstractions that enhance operational excellence, including observability, quota management, failure recovery, and developer ergonomics.
- Act as a technical mentor for both senior and junior engineers, elevating design quality, code health, and engineering rigor.
- Partner with engineering managers and product leaders to translate business goals into executable technical strategies.
- Proactively identify and resolve systemic production issues, driving durable fixes rather than tactical mitigations.
Qualifications
Required Qualifications:
- Bachelor's Degree in Computer Science or a related technical field AND hands-on experience in coding with languages such as C, C++, C#, Java, JavaScript, or Python OR equivalent experience.
- Proven experience in designing and operating large-scale distributed systems in production.
- Demonstrated ability to lead technical decisions across multiple teams or services.
Other Requirements:
Ability to meet Microsoft, customer, and/or government security screening requirements is essential for this role. This includes—but is not limited to—the following specialized security screenings:
- Microsoft Cloud Background Check: This position will be required to pass the Microsoft Cloud background check upon hire/transfer and every two years thereafter.
Preferred Qualifications:
- Master's Degree in Computer Science or a related technical field AND 8+ years of technical engineering experience with coding in languages such as C, C++, C#, Java, JavaScript, or Python OR a Bachelor's Degree in Computer Science or a related technical field with extensive technical engineering experience with coding in those languages OR equivalent experience.
- Experience building platform or infrastructure services in cloud environments (Azure preferred).
- Deep understanding of multi-tenant architectures, security boundaries, and privacy-compliant system design.
- Hands-on experience with Azure Machine Learning, Kubernetes, GPU-backed workloads, or large-scale data pipelines.
- Track record of driving architecture simplification, reliability improvements, and cost efficiency at scale.
- Ability to operate effectively in high ambiguity, influencing without authority and earning trust across organizational boundaries.
How to Apply
To be considered for this position, please apply online using the form below. Only applications matching the job profile will be considered.
Microsoft is an equal opportunity employer. All qualified applicants will receive consideration for employment without regard to age, ancestry, citizenship, color, family or medical care leave, gender identity or expression, genetic information, immigration status, marital status, medical condition, national origin, physical or mental disability, political affiliation, protected veteran or military status, race, ethnicity, religion, sex (including pregnancy), sexual orientation, or any other characteristic protected by applicable local laws, regulations, and ordinances.
If you need assistance with religious accommodations or a reasonable accommodation due to a disability during the application process, please read more about requesting accommodations.