A retailer needs a release with no user-visible downtime, and it wants traffic restored to the previous version within seconds if the new one misbehaves. It accepts running double capacity during the switch. Which approach fits?
Show answer and explanation
Answer: C
A blue/green deployment runs two production-grade environments. The new version is deployed and verified in the idle environment, then traffic is switched to it in one step. If problems appear, traffic can be pointed back at the previous environment immediately, which gives fast rollback with no downtime. The cost is running two environments during the switch. Rolling updates and percentage rollouts reduce exposure gradually but rely on replacing instances or shifting traffic over time, and recreate causes downtime.
Why the other options are wrong
- A. A rolling update replaces instances gradually, so old and new versions run together and rollback means another rolling pass. That is slower than a traffic switch and does not match the seconds-level reversal the retailer requires.
- B. Recreate stops the old version before starting the new one, so users experience downtime. The retailer explicitly rules out downtime, which makes this approach unsuitable.
- D. A multi-day percentage rollout limits exposure gradually but does not provide an instant full rollback path. It also fails the requirement to revert within seconds across all traffic.