Which CodeDeploy configuration should the solutions architect use?

Explanations:

A blue/green deployment creates a completely new environment (the “green” environment) and switches traffic to it once it’s ready. While this allows for easy rollback, it’s not the best approach for testing with a subset of users before a full deployment. It’s more suitable for minimizing downtime during full deployments.

A linear deployment releases the new version in equal increments with a specified wait time between each increment. While it provides some level of controlled rollout, it’s not designed for testing with a specific subset of users.

A canary deployment releases the new version to a small subset of users (the “canary”) before rolling it out to the rest. This allows for testing the new version in a real-world environment with limited impact if issues are found. It also provides an easy rollback mechanism by simply redirecting traffic back to the original version. This meets all the requirements.

An all-at-once deployment releases the new version to all users simultaneously. This offers no opportunity for testing with a subset of users or a simple rollback mechanism.