Postmortem: Python 3.13 C Extension Crash Due to Rust 1.85 FFI Error On March 15, 2024, our production environment experienced a total outage of our core data processing pipeline, traced to a segmentation fault in a Python 3.13 C extension that interfaced with Rust 1.85 compiled code via FFI. This postmortem details the incident timeline, root cause, and key takeaways for teams building cross-language FFI integrations. Incident Summary Our data processing pipeline relies on a Python 3.13 C extension to invoke high-performance mathematical routines written in Rust, with communication via the C FFI. Following a routine Rust toolchain update to version 1.85, the extension began experiencing intermittent segmentation faults in staging, which were misclassified as flaky test failures. A production deploy at 10:30 UTC triggered a full outage: the extension crashed on all worker nodes, halting all job processing.…