certinfo: How One Developer Built a Zero-Dependency TLS Certificate Monitor in Rust

TLS certificate expiration is one of the most predictable yet preventable causes of production outages, typically caught only when systems fail catastrophically. certinfo addresses this by providing a lightweight alternative to complex tools like openssl s_client and blackbox_exporter: a statically-compiled Rust binary with no external dependencies. With three-value exit codes and JSON output, it integrates seamlessly into cron jobs and CI/CD pipelines for real-time certificate monitoring.