Principal Software Engineer

Principal Software Engineer

Microsoft Suisse Sàrl Vacant since : 05.02.2026 Number of jobs : 1 1214 Vernier (GE) 100% Immediately Permanent

Microsoft 365 Copilot is transforming productivity by integrating large language models with user data, Microsoft Graph, and the web. At the core 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, One Note, and beyond.

Our team is pioneering the infrastructure for tenant‑isolated fine‑tuning, a foundational platform capability that enables customers to safely personalize Copilot agents 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 own the end‑to‑end fine‑tuning platform via Heron, spanning:
Data extraction and isolation;
Secure training and evaluation workflows;
Model deployment, migration, and lifecycle management. Our systems operate at massive scale in multi‑tenant environments, enforce strict security and compliance boundaries, manage shared GPU resources effectively, and enable seamless onboarding of new models and customers. As a Principal Software Engineer, you will play a critical 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 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 directly 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.

Microsoft’s mission is to empower every person and every organization on the planet to achieve more. As employees we come together with 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 create a culture of inclusion where everyone can thrive at work and beyond.

• 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 driving alignment across multiple organizations.
• Build frameworks and abstractions that improve operational excellence, including observability, quota management, failure recovery, and developer ergonomics.
• Act as a technical mentor for senior and junior engineers, raising the bar on 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.

• Required Qualifications: Bachelor s Degree in Computer Science or related technical field AND hands on technical engineering experience with coding in languages including, but not limited to, C, C++, C#, Java, JavaScript, or Python OR equivalent experience.
• Proven experience designing and operating large‑scale distributed systems in production.
• Demonstrated ability to lead technical decisions across multiple teams or services.

• Other Requirements: Ability…