Blue Green Cutover Time Calculator

Work out blue green cutover time instantly with clear inputs, formula shown and shareable results.

About Blue Green Cutover Time Calculator

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.

Formula

Cutover timing

environment ready = warm-up + health confirmation (in parallel across instances); cutover = ready + switch time; rollback = switch time

Worked example

With the default values below, Blue Green Cutover Time Calculator returns Total cutover time of 140. Change any input above and every figure here is recalculated in your browser.

Inputs used

Instances in the target environmentminimum 1: 24
Warm-up per instanceminimum 0 s: 90 s
Health check confirmationminimum 0 s: 30 s
Load balancer or DNS switchminimum 0 s: 20 s

Results

Total cutover time: 140 s
Time to get the green environment ready: 120 s
Time to roll back: 20 s
Instances running during cutover: 48

Step by step

1Values used
2Cutover timing
3Total cutover time= 140 s
4Time to get the green environment ready= 120 s
5Time to roll back= 20 s
6Instances running during cutover= 48

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why prefer a load balancer switch over DNS?

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.

What breaks blue-green in practice?

Shared state, especially database schema changes. The two environments must both work against one database, which forces backwards-compatible migrations.