Also called Canary release, Canary deployment, Gradual rollout
Sending a small share of real traffic to the new version, comparing it with the old one, and only then sending everyone. If it is bad, few people met it.
Some problems appear only under real traffic, and a canary limits how many people find them. It only helps if you can tell in time, which takes enough requests and a real comparison. A tiny canary on a quiet site tells you nothing.
Say it to your agent
“Deploy with wrangler versions deploy at 10%, and compare its 5xx rate with the old version's for 15 minutes. At 1,000 requests a minute, 10% is enough to judge. If it is worse, go back to 0% and tell me. If not, go to 50%, then 100%. "No alerts fired" doesn't count as a pass.”