What is the best strategy for applying a critical security patch while minimizing customer impact?

Performing a canary rollout of the security patch is an effective strategy for minimizing customer impact while applying a critical security patch. This approach involves deploying the patch to a small subset of instances first—essentially a "canary" group—before rolling it out to the entire environment.

This allows teams to monitor the performance and stability of the application after the patch is applied to this limited scope. If any issues arise, they can be addressed promptly without affecting all users. The canary rollout provides valuable data on how the patch performs in production, enabling teams to make informed decisions before proceeding with a broader deployment.

In contrast, updating all Compute Engine instances simultaneously could lead to significant outages or disruptions if the patch introduces any unforeseen issues. Scheduling a 24-hour rolling update during overnight hours may reduce customer impact, but there's still a risk of affecting users if the update causes problems during the rollout. Similarly, implementing an A/B rollout involves maintaining two environments and directing user traffic between them; while it allows testing different versions, it does not specifically focus on a security patch application in a controlled manner.

Overall, the canary rollout is tailored for safely applying updates, making it the best choice for a critical security patch with minimal disruption.