Inside Microsoft’s Rust Revolution: A CTO’s Vision for Safer Code

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At the Rust Nation UK conference, Mark Russinovich, Microsoft’s CTO of Azure, delivered a bold message: Rust isn’t just a new tool — it’s the future of Microsoft’s systems programming.

We broke down the key takeaways from his talk in this edition.

Let`s explore how this will impact you.

"70% of our vulnerabilities came from C/C++", Russinovich

Microsoft’s security data from the past decade shows that the vast majority of critical bugs stemmed from memory safety issues, especially in C and C++. That’s what triggered Microsoft’s move.

“Rust is ready. We should just be switching to Rust.” — Mark Russinovich, CTO, Microsoft Azure

According to Russinovich, Rust enforces correctness, avoids entire classes of bugs at compile time, and improves developer confidence.

How Microsoft Is Using Rust Today

1. Windows Internals

• Project Mu: UEFI firmware rewritten in Rust, now in Surface laptops and Azure data centres.
• DirectWrite: 154,000+ lines of C++ ported to Rust — eliminating known font parser vulnerabilities and improving performance by up to 15%.
• Win32k.sys: Security-critical subsystems like GDI regions are now written in Rust.

“We never saw a performance regression — only gains.”

2. Azure Infrastructure

• All new system code is written in Rust by default.
• Security modules, firmware, and networking agents are being rebuilt in Rust, including Microsoft’s distributed HSM system.

3. Office & Data Platform

• Rust powers vector search and indexing in Office’s backend, outperforming C++ while cutting memory usage.
• Azure Data Explorer’s core logging engine: now 350,000+ lines of Rust.

From C++ to Rust: Powered by AI

To speed things up, Microsoft is using GraphRAG, a combination of AI and graph-based retrieval, to translate legacy C/C++ to Rust. They’ve even developed a verified transpiler for cryptographic code.

“The faster we can get off C/C++, the better.”

Russinovich demoed side-by-side translations, showing how AI can port complex codebases to safe, performant Rust.

Developer Feedback Inside Microsoft

What teams love:

• Fewer bugs and memory issues
• Improved performance, even without optimisation
• “If it compiles, it works”

What’s still tricky:

• C++ interop is painful
• Dynamic linking in Windows
• Choosing reliable crates from a still-maturing ecosystem

“Two months in, developers go from ‘this is hard’ to ‘I love it.’”

You can watch the full keynote here to hear Mark Russinovich explain it all first-hand.

Let us know your thoughts, we’d love to hear how you’re approaching Rust in your work.

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