Canary Releases

A canary release sends a small slice of production traffic to a new version, watches what happens, and only continues if the metrics look good. Named after the canaries miners carried to detect dangerous gases: a small subject goes in first, and the rest follow only if it survives.

This is the most controlled deployment strategy in common use. It costs more than rolling, demands more operational machinery than blue-green, and requires real metrics discipline. The payoff is that high-risk changes can ship without exposing the whole user base to a bad version.