KCNA Cloud Native Application Delivery Practice Question
In a blue-green deployment strategy, at any given time, only one environment (blue or green) is active. What is the primary advantage of this approach?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Instant rollback by switching traffic back to the previous environment
Blue-green deployments allow instant rollback by switching traffic back to the previous environment. This is the primary advantage: if issues arise in the new version, you can immediately revert by pointing the router/load balancer to the old environment. Option A describes gradual traffic shifting, which is characteristic of canary deployments, not blue-green. Option C is incorrect because blue-green requires two full environments, doubling resource consumption. Option D is false because a load balancer or ingress controller is essential to switch traffic between the two environments.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Gradual traffic shifting to detect issues early
Why it's wrong here
Gradual traffic shifting describes canary releases, which incrementally route a percentage of requests to the new version. Blue-green switches all traffic at once after the green environment is verified, so issues surface only post-cutover. Canary deployment is the correct choice when early detection through partial exposure is required.
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Instant rollback by switching traffic back to the previous environment
Why this is correct
Because the previous environment remains fully deployed and idle, reverting is simply a matter of repointing the router or load balancer, giving near-instantaneous rollback. This satisfies the stem's single-active-environment constraint while minimising downtime risk during release.
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Minimal resource consumption by using only one environment
Why it's wrong here
Blue-green deliberately runs two full environments simultaneously, doubling compute, memory and storage during the transition, so resource consumption is higher, not minimal. Minimal footprint is achieved by in-place or rolling updates, which reuse existing capacity. The blue-green benefit is instant rollback and zero-downtime cutover, not economy.
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No need for load balancers or ingress controllers
Why it's wrong here
Blue-green still requires a load balancer or ingress controller to switch traffic between the blue and green environments; the router is the mechanism performing the cutover. Omitting it is impossible. Load balancers are genuinely unnecessary only in single-environment setups where no traffic split or switchover between versions occurs.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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