Work out blue green cutover time instantly with clear inputs, formula shown and shareable results.
Blue-green warms the whole new environment in parallel, so instance count does not extend the warm-up — it only doubles the capacity bill for the duration. The cutover itself is a single load balancer or DNS change, which is also the rollback, and that symmetry is the strategy's main advantage: reverting takes the same seconds as switching.
Cutover timing
environment ready = warm-up + health confirmation (in parallel across instances); cutover = ready + switch time; rollback = switch time
DNS is subject to client and resolver caching that ignores TTL, so some traffic keeps hitting the old environment for far longer than expected. A load balancer switch is immediate and deterministic.
Shared state, especially database schema changes. The two environments must both work against one database, which forces backwards-compatible migrations.