CV0-004 Deployment Practice Question
A company wants to deploy a new version of a web application with zero downtime. They decide to use a blue/green deployment strategy. Which action is essential to switching traffic from the blue environment to the green environment?
⚠ Common exam trap
Exam takers often confuse the distinction between DNS-based traffic switching (which has propagation delays and is not instantaneous) and load balancer configuration updates (which provide immediate, atomic traffic shifting), leading them to incorrectly choose DNS modifications for zero-downtime blue/green deployments.
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
✓
Update the load balancer target group to point to the green environment
In a blue/green deployment, the load balancer is the traffic router. Updating the load balancer target group to point to the green environment is essential because it instantly shifts production traffic from the blue (current) to the green (new) environment without downtime. This action ensures the load balancer forwards requests to the healthy green targets, completing the cutover.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Scale down the blue environment before traffic is switched
Why it's wrong here
Scaling down before switching would cause downtime if the green environment fails.
- ✗
Deploy a canary release that sends 10% of traffic to green first
Why it's wrong here
That describes a canary deployment, not blue/green.
- ✓
Update the load balancer target group to point to the green environment
Why this is correct
Correct. Changing the load balancer routing effectively shifts traffic.
- ✗
Modify the DNS TTL to 0 and update A records
Why it's wrong here
DNS changes can be used but are not as immediate as load balancer updates; they can cause propagation delays.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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