ACP-Cloud1 Exam Dumps : ACP Cloud Computing Certification

According to the Alibaba Cloud ECS documentation1, the Pay-As-You-Go billing method is flexible and suitable for short-term or uncertain workloads. However, it is also the most expensive option compared to other billing methods. To reduce the cost of Pay-As-You-Go instances, you can purchase a Savings Plan, which is a discount plan that offers lower prices for a fixed amount of hourly usage. A Savings Plan can be applied to any Pay-As-You-Go instance in the same region, regardless of the instance type, operating system, or zone. Therefore, option A is the most cost-effective billing method for a 10-day test, as it allows you to enjoy the flexibility of Pay-As-You-Go and the savings of a fixed commitment. References: Billing methods and Savings Plan.

RDS provides whitelist access policies. You can set permitted IP addresses and IP network segments to effectively prevent hackers from attacking the server by port scanning1. A whitelist is a list of IP addresses or CIDR blocks that are allowed to access an RDS instance. By default, the whitelist is empty, which means that no IP address can access the RDS instance. You can add IP addresses or CIDR blocks to the whitelist to allow access from specific sources. You can also modify or delete the whitelist as needed2. Whitelist access policies help improve the security of your RDS instance and protect your data from unauthorized access3. 

 To execute a task at a specific time such as removing 1 ECS instance every night at 00:00, you need to perform two operations: create a scaling rule and create a scheduled task. A scaling rule is a set of instructions that defines how Auto Scaling scales computing resources in response to changes in business load. A scheduled task is a type of scaling task that can execute a specified scaling rule at a specified time. By creating a scaling rule that removes 1 ECS instance from the scaling group, and creating a scheduled task that executes this scaling rule every night at 00:00, you can achieve the desired result. You do not need to create a new scaling group, because you already have one scaling group created. You also do not need to create an event-triggered task, because this type of scaling task is triggered by events such as Cloud Monitor alarms or API calls, not by a specific time. References: 1, 2, and 3.