Meta Platforms is undergoing a major migration of its mobile and messaging infrastructure—from long-standing C code to Rust. The rewrite affects core libraries used across Facebook, Messenger, Instagram, Instagram Lite, VR headsets, and wearables—touching billions of daily users
Why Meta Is Making the Switch
Memory Safety & Reliability
Engineers say the legacy C code had become “spaghetti”—manual memory management, long functions, and risky refactors that often led to hard-to-debug production incidents. Rust’s ownership and borrow checker enforce memory safety at compile time, preempting use-after-free and data-race bugs
Developer Productivity & Happiness
Meta engineers report faster feedback, deterministic formatting via rustfmt, and integrated tooling (rust-analyzer) that significantly improves iteration speed, readability, and confidence. They emphasize improved developer velocity and confidence over raw performance metrics alone
Supporting Rust at Meta
Meta officially supports Rust as a primary server-side language alongside C++, Python, and Hack. Rust is strongly recommended for performance-critical services, CLI tools, and backend systems that demand safety and reliability
Meta has built resources—like internal bootcamps, Rust working groups, and cxx interoperability tools—for easier migration and collaboration across C++ and Rust code
Migration in Practice
Meta’s Messaging Infrastructure team is leading the rewrite of its legacy C library into Rust, even though most engineers started with minimal Rust experience. Through one-on-one coaching and code reviews, the rewrite has become a shared mission, fostering a growing internal Rust ecosystem
Debugging support now extends seamlessly across mixed C/Rust stacks, allowing breakpoints to navigate into Rust frames with full visibility—an experience previously unavailable in mixed-language codebases
Broader Trends in Tech
Meta is part of a larger wave of major tech firms adopting Rust for safer systems code:
- Google, Microsoft, AWS, and Cloudflare are increasingly migrating performance-sensitive components from C++ or C to Rust for memory safety and developer productivity benefits
- Rust is now widely recognized as an industry-grade language especially for backend services, embedded systems, and concurrent codebases
Risks and Challenges Ahead
- Learning curve: Rust can initially be steep—engineers report nightmares of the borrow checker—but Meta’s collaborative culture and tooling support are helping ease onboarding
- Migration scope: Rewriting decades of C code is massive. Execution risks include integration complexity, parity with legacy behavior, and maintaining performance across mixed stacks.
- Adoption trade-offs: Some teams still rely heavily on C/C++ for embedded or specialized domains where rewrite cost may outweigh benefits
✅ Conclusion
Meta’s decision to migrate its mission-critical messaging runtime from C to Rust reflects a strategic bet on memory safety, long-term maintainability, and engineering happiness. As the rewrite gains momentum, Meta joins industry peers in redefining systems development standards—prioritizing resilience over historical inertia. With Rust tooling and internal support maturing rapidly, Meta’s switch may become a model case for large-scale adoption of modern safe languages.
