CI/CD & DevOps Practices Practice Question 4: Canary vs Blue Green
CI/CD & DevOps Practices · Test 1 · question 4 of 10
A team is releasing a major rewrite of its search service. It wants the new version to serve real production traffic first for a hand-picked group of users (internal staff), then for a growing share of customers, and to compare the new version's error rate with the old version's at every step. If problems appear, the team must be able to send the affected users back to the old version. The team cannot pay for a second full-size copy of production.
Which deployment strategy fits these requirements?
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Answer:
A canary release deploys the new version to a small part of the infrastructure first. It routes a few selected users to it, then moves more users over as confidence grows. Running both versions side by side lets the team compare the new version with the old one, and rolling back is just routing users back to the old version. It needs only the extra capacity the canary uses, so it meets every constraint (C).
Option A needs two identical production environments, which the team cannot pay for. Its switch also moves all traffic at once, so there is no stage for staff only or for a growing share of customers.
Option B does expose the new version gradually, but which users land on it depends on whichever instances have been replaced, not on who the users are. It cannot aim at internal staff first, and it offers no controlled per-version comparison.
Option D takes the whole service down and brings everyone onto the new version at once. It has no gradual exposure and no quick way back.
References: Canary Release (Martin Fowler); Blue Green Deployment (Martin Fowler)