Ways to release.
WHAT A ROLLING UPDATE IS
Replacing instances gradually.
WHAT IT PROVIDES
No downtime, with modest extra capacity.
WHAT IT COSTS
Both versions running simultaneously.
WHAT THAT REQUIRES
Compatibility between them, particularly in the database.
WHAT A BLUE-GREEN DEPLOYMENT IS
Two complete environments, with traffic switched between them.
WHAT IT PROVIDES
Instant switching, and instant reversal.
WHAT IT COSTS
Double the infrastructure during the change.
WHAT A CANARY RELEASE IS
Sending a small proportion of traffic to the new version.
WHAT IT PROVIDES
Real evidence before full exposure.
WHAT IT REQUIRES
Traffic splitting Metrics good enough to compare
WHY THAT SECOND POINT MATTERS
Without comparison, a canary is just a slower rollout.
WHAT TO COMPARE
Error rate and latency, between versions.
WHAT TO AUTOMATE
Rolling back when the new version performs worse.
WHAT A FEATURE FLAG ADDS
Separating deployment from release.
WHY THAT IS POWERFUL
Code can be deployed inactive, and enabled or disabled without a deployment.
WHAT TO CHOOSE FOR MOST TEAMS
Rolling updates, with feature flags for risky changes.
WHAT TO AVOID
Complexity exceeding what the risk justifies.
