Canary

Dynamic configuration (config store, runtime re-read); feature flags (progressive rollout, A/B testing, kill switch, deployment-release decoupling); operational triad: monitor → observe → manage

Correctness verification: both implementations run per request; old result returned; GitHub Scientist; dark launching vs canary vs parallel run; progressive delivery

Release in stages exposing change to controlled subsets; deployment vs release decoupling; canary/blue-green/ring/dark-launch/parallel-run/feature-flag spectrum; SRE order-of-fault model; "roll back first, diagnose second"; prerequisites and anti-patterns

Zero-MTTR via pre-production testing; traditional test hierarchy; production tests (config tests, stress tests, canary); production probes; barrier defence pattern; configuration file risk management