What progressive delivery means
Progressive delivery separates deployment (code in production) from release (users seeing new behaviour). Every technique below lets you control who sees what, and roll back instantly if metrics degrade.
Dark launching
New code runs in production but its output is discarded. The old code still serves the response. Used to: test performance under real load, warm up caches, and validate correctness before users see the new path. No user impact on failure.
Canary releases
Route a small percentage (1–5%) of traffic to the new version. Monitor error rate, P99 latency, and business metrics for 15–30 minutes. If metrics are stable, increase traffic. Automated rollback if a threshold is crossed.
Feature flags for user targeting
Enable for internal users first. Then beta users. Then 1% of all users, 10%, 50%, 100%. At each stage, monitor for regressions. This is the safest rollout path for high-risk changes.
Rollback strategy
The value of progressive delivery is fast rollback. Turning off a feature flag takes seconds. A canary shift-back takes under a minute. Design your release process so rollback is faster than the incident response time.