After a tax-site blue-green cutover, why keep the prior (blue) environment as an idle standby?
Select an answer to reveal the explanation.
Short Explanation
You keep blue as a standby so you can quickly send citizens back if the green tax release misbehaves. Wiping blue the same hour removes that fast way to undo the cutover.
Full Explanation
After a blue-green cutover, you retain the prior (blue) environment briefly as an idle standby so operators can switch traffic back quickly if the new (green) release misbehaves. For a tax site, blue is the fast undo path while you watch green under real citizen load. Keeping blue ready is part of the blue-green value proposition, not optional cleanup theater. Permanently powering off and wiping blue the same hour destroys the rapid rollback target immediately after cutover. Randomly load-balancing citizen sessions without rollback intent misses the purpose of the idle standby: blue-green supports a controlled switchback, not aimless balancing that mixes versions without a rollback plan. Denying auditors a previous-version environment also misses the purpose: the standby exists to restore service, and preventing inspection is not a delivery goal. Exam caveat: retaining blue forever may be costly; the point is to keep it through the validation window so rollback remains a traffic flip. Decommissioning blue after green is proven is normal, just not in the same hour as cutover, when fast switchback may still be required. Practical check: after cutover, verify idle blue still passes health checks, rehearse a switchback, and schedule teardown only after the soak window and rollback criteria are met.