Google Cloud Certified Associate Cloud Engineer Practice

You've been running your App Engine app for a few weeks with Autoscaling, and your marketing team is planning a massive campaign. How would you ensure there are always 4 idle instances?

1. Set the min_instances property in the app.yaml

2. Switch to manual scaling and use the burst_traffic_protection property to True in the app.yaml.

3. Set the min_idle_instances property in the app.yaml.

4. Switch to manual scaling and use the idle_instance_count property in the app.yaml.

The correct answer is: Set the min_idle_instances property in the app.yaml.

To ensure there are always four idle instances in your App Engine app, setting the `min_idle_instances` property in the `app.yaml` configuration file is the correct approach. This property specifies the minimum number of idle instances that should be kept ready to handle incoming requests without any delay, which is particularly beneficial during peak traffic times, such as during a large marketing campaign. By maintaining a threshold for idle instances, you can effectively preserve responsiveness and manage load during fluctuations in user demand. The other options do not achieve the same goal. While setting `min_instances` defines a minimum number of total instances (both active and idle), it doesn’t ensure a specific count of idle instances. Switching to manual scaling changes how the app scales and won't guarantee idle instances without additional configurations. The `burst_traffic_protection` and `idle_instance_count` properties, while relevant, do not specifically focus on maintaining a set number of idle instances as desired for this scenario.