Principal Software Engineer

Microsoft 365 Substrate is the shared data and intelligence platform behind Exchange, SharePoint, OneDrive, Teams and Microsoft 365 Copilot. It stores, indexes, secures and serves content for hundreds of millions of users across a global fleet, and it is the foundation on which search, semantic retrieval and AI experiences are built. Every email, file, message and permission change flows through the platform's storage, ingestion and propagation layers before customers can find and use it.

We are looking for engineers who want to build and run systems at this scale. In this role you will design, ship and operate core services across the Substrate stack: storage and data-access services, large-scale ingestion and propagation pipelines, search indexing and freshness, and the observability and repair systems that keep customer data correct and current. You will own production quality end to end, from architecture and code to deployment, on-call and continuous improvement.

The role is intentionally broad so that solid engineers can grow across the stack, with particular emphasis on Substrate storage. Engineers who bring deep storage and data-systems expertise will find significant room to shape how content is partitioned, scaled, repaired and served for Microsoft 365 workloads.

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.

Responsibilities

• Design, build and operate highly available distributed services on the Substrate platform, with clear ownership for reliability, performance, security and cost.
• Evolve storage and data-access services, including client SDKs and APIs, migration from legacy access paths to supported clients, and correctness guarantees for reads, writes, deletes and queries.
• Build and modernize large-scale ingestion and propagation pipelines, including event-driven processing, queueing, prioritization, retry, flow control and backpressure, so that content and permission changes reach downstream systems quickly and reliably.
• Improve search freshness and completeness by tracing data end to end, detecting gaps, and building safe, replay-able and idempotent repair and backfill mechanisms.
• Drive scale and capacity work across shards and stamps (groups of shards managed as a unit), including scale-out, scale-up, rebalancing, in-place repartitioning and approaches that avoid costly full re-crawls of source data.
• Diagnose and mitigate production issues involving throttling, CPU, memory and disk pressure, hot spots, regional capacity constraints and cross-service dependencies, then deliver sustainable fixes.
• Build observability: metrics, logs, traces, dashboards, alerts and data-quality pipelines that distinguish real customer impact from reporting gaps.
• Raise engineering quality through design reviews, automated and functional testing, safe flighting and rollback, and reduction of test flakiness and toil.
• Apply automation and AI-assisted tooling to incident triage, diagnostics and routine operations.
• Partner with service teams across regions and time zones to plan milestones, onboard new workloads and land cross-team architectural changes.

Qualifications

Required Qualifications:

• Bachelor's Degree in Computer Science or related technical field AND 6+ years technical engineering experience with coding in languages including, but not limited to, C, C++, C#, Java, JavaScript, or Python OR equivalent experience.

Other Requirements:

Ability to meet Microsoft, customer and/or government security screening requirements are required for this role. These requirements include but are 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:

• Bachelor's degree in Computer Science or a related technical field, or equivalent practical experience.
• Typically 5+ years of professional software engineering experience for Senior, and 8+ years for Principal, building and shipping backend or infrastructure software. Equivalent demonstrated impact is considered.
• Solid coding skills in at least one systems or backend language such as C#, C++, Java, Go or Rust. Experience with C# and .NET is especially relevant; equivalent experience transfers well.
• Solid foundations in data structures, algorithms, concurrency, networking and operating systems.
• Experience designing and operating distributed systems or cloud services, including reasoning about failure modes, consistency, latency and throughput.
• Experience designing APIs or SDKs, writing testable code and building automated tests at unit, integration and end-to-end levels.
• Experience running production services, including participation in on-call rotations, incident response and root-cause analysis.
• Clear written and verbal communication in English, including design documents and status updates for technical and leadership audiences.
• 8+ years building large-scale distributed storage, database, search or messaging systems (Principal), or 5+ years with significant ownership in one of these areas (Senior).
• Hands-on experience with storage engines, distributed file or object stores, key-value stores, or search engines such as Lucene-based systems.
• Experience operating services at the scale of millions of tenants or billions of items, including multi-region and sovereign-cloud deployments.
• Experience with Microsoft 365, Exchange, SharePoint or OneDrive back ends, or with Azure Storage, Cosmos DB or similar platforms.
• Experience leading a major migration, re-architecture or modernization of a production system with no customer-visible disruption.
• Track record of publications, patents, open-source contributions or internal technical talks in distributed systems or storage.

#CAP #M365

This position will be open for a minimum of 5 days, with applications accepted on an ongoing basis until the position is filled.

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 and/or a reasonable accommodation due to a disability during the application process, read more about requesting accommodations.