Blue-green deploy
Blue-green deployment maintains two identical production environments — blue (current) and green (new). Releases deploy to green; once health checks pass, traffic flips from blue to green. Rollback is instantaneous: flip the router back to blue.
Blue-green is the simplest deploy strategy for zero-downtime releases. Trade-offs: requires running 2x infrastructure during the cutover; database schema changes need to be backwards-compatible so blue can still serve traffic on the new schema; long-running connections may break at flip time. Modern variations (canary, rolling) often replace pure blue-green for non-trivial systems but the concept remains foundational.
Related terms
- Canary release
A canary release routes a small percentage of production traffic (typically 1-5%) to a new version, monitors error rates and latency, and rolls forward to 100% only when metrics stay healthy.
- Continuous deployment
Continuous deployment automatically deploys every change that passes the test suite into production — no human gate between merging code and serving traffic.
- Feature flag
A feature flag is a runtime toggle that gates whether a code path is active.