What is a Principal Engineer at Microsoft?

The gap between senior and principal engineer is not about technical skill. It is about scope and the willingness to lead change. When a senior engineer encounters a problem, they identify it and propose a solution. When a principal-level engineer sees the same problem, they devise solutions, pick one, and implement it. Then they ask others to join and influence a group of more than 10 people, formally or informally. That is the mindset shift that matters.

Dejan Dunjerski replatformed Azure SQL Managed Instance without customers noticing while scaling the service by a factor of 10. Before that, he built an AI troubleshooting system for millions of databases when no one in academia had researched the problem. His career path shows what principal-level work looks like in practice: building a proof of concept for Azure's first open-source database in two months, conducting research in unrelated fields when no existing solutions exist, and running a live service through a replatforming effort where every dependency timeline is unreliable. The non-technical challenge is harder than the technical one. You have to negotiate, ask for support, and influence teams that do not report to you.

Simplicity is the guiding principle. Start with the simplest possible solution, then figure out what needs to change and where. Workarounds compound. The usual trap is starting from what you have now and modifying it slightly, then after three iterations you end up with 10 times more complex code that no one understands. Instead, understand the problem, find the best place to solve it, and figure out why you cannot solve it there immediately. Making a change in the right place or resolving the blocker pays off. Dunjerski avoids short-term workarounds and plans beyond sprints. When dependencies slip, sometimes helping the dependency team delivers faster than waiting.

For the areas you own, you need to know the details. The devil is in the details and those details will bite you. Before making a decision on one project, Dunjerski examined the Windows codebase to understand how Windows containers work. That understanding helped him influence his team and other teams. Other useful practices include data science analysis of logs and using dashboards to get a broad view that helps you focus on the most important aspects. Breadth matters, but depth in your domain prevents surprises.