A and C are the correct answers because they can improve the performance of the platform by reducing the load on the ECS instances and the database server.

A is correct because using CDN can accelerate the delivery of static content such as CSS and JavaScript files, which can reduce the bandwidth consumption and latency of the ECS instances.  CDN can also cache the content in edge nodes closer to the end users, which can improve the user experience and response time of the platform 1

C is correct because using RDS can replace the existing self-built database, which can provide better database performance, reliability, security, and scalability. RDS can also handle the backup, recovery, monitoring, and maintenance of the database, which can reduce the management overhead and cost of the platform.  Moreover, creating RDS read-only instances can handle read-only requests, which can reduce the workload on the master RDS instance and improve the database availability and performance 2 3

References :  1 :  CDN Overview   2 :  RDS Overview   3 :  RDS Read-only Instances

Server Guard is a cloud-based security service that provides real-time protection for servers against intrusion events, such as brute force password cracking. Server Guard consists of a lightweight agent that is installed on the server and a cloud protection center that analyzes and responds to security threats.  Server Guard can help the administrator to reduce the possibility of brute force password cracking by providing the following features 1 :

Password cracking protection : Server Guard can detect and block password cracking attempts on servers, such as SSH brute force attacks on Linux servers and RDP brute force attacks on Windows servers. Server Guard can also alert the administrator of the attack source, time, and frequency, and provide suggestions for password strengthening.

Webshell detection and removal : Server Guard can scan and remove webshells that are maliciously implanted on servers by hackers. Webshells are scripts that allow hackers to remotely execute commands on servers, such as stealing data, uploading files, or launching attacks. Server Guard can identify and delete webshells based on signature matching, behavior analysis, and machine learning.

Anti-virus and anti-ransomware : Server Guard can detect and terminate various types of malware, such as ransomware, mining programs, backdoor programs, worms, and trojans. Server Guard can also prevent the encryption and deletion of files by ransomware, and restore the files to their original state.

Security baseline check : Server Guard can perform security baseline checks on servers to evaluate their security posture and compliance level. Server Guard can check more than 40 security items, such as system configuration, account management, network security, and log audit. Server Guard can also provide security hardening suggestions and one-click fixes for the detected issues.

Security situation awareness : Server Guard can provide a comprehensive and visualized view of the security situation of the servers, such as the number of attacks, the attack sources, the attack types, the attack trends, and the security score. Server Guard can also provide security reports and recommendations for improving the security level of the servers.  References:   Security Center

Server Load Balancer (SLB) is a service that distributes traffic among multiple ECS instances to improve the service capabilities of applications. SLB monitors the health of ECS instances in real time and automatically isolates unhealthy instances from the server pool according to the configured health check policy. This ensures that the traffic is only forwarded to healthy instances, thereby improving the availability and fault tolerance of applications.  References :  ACA Cloud Computing Certification - Alibaba Cloud Academy ,  E-Learning Courses - Alibaba Cloud Academy , Server Load Balancer - Alibaba Cloud Documentation Center

When using Alibaba Cloud OSS, you can set access control in three different levels, which are bucket level, object level, and RAM account level. Bucket level access control is the highest level of access control, which determines whether a user can access the bucket and its objects. Bucket level access control can be set to public read/write, public read, or private. Object level access control is the second level of access control, which determines whether a user can access a specific object in the bucket. Object level access control can be set to inherit from the bucket, public read/write, public read, or private. RAM account level access control is the lowest level of access control, which determines whether a user can perform certain operations on the bucket or the object. RAM account level access control can be set by using RAM policies, which specify the actions, resources, and conditions for the access.  References :  Object Storage Service (OSS) - Alibaba Cloud Academy ,  Access Control - Alibaba Cloud Documentation Center

 = A is the correct answer because the memory size of an ECS instance is determined by the instance type, and it cannot be changed independently.  If you want to change the memory size of an ECS instance, you must change the instance type to another one that has a different memory size 1 2

B, C, and D are incorrect answers because the system disk size, data disk size, and number of data disks of an ECS instance can be changed without changing the instance type.  You can use the ECS console or API to resize the system disk or data disks of an ECS instance, or add or remove data disks from an ECS instance 3 4 5 6

References :  1 :  Overview of instance families   2 :  Change the instance type   3 :  Resize disks   4 :  Resize a disk   5 :  Attach or detach data disks   6 :  Attach or detach a data disk

Alibaba Cloud does not support intranet communication between products that are not in the same region, which means that ECS instances in different regions cannot communicate with each other on the intranet, and ECS instances and other products in different regions, such as ApsaraDB for RDS and OSS instances, cannot communicate with each other on the intranet. However, this does not mean that Server Load Balancer cannot be deployed for ECS instances in various regions. Server Load Balancer is a service that distributes traffic among multiple ECS instances according to the configured forwarding rules. It can be used to balance the load and improve the service availability and fault tolerance of applications.  Server Load Balancer supports cross-region deployment, which means that it can distribute traffic to ECS instances in different regions 1 2 .  References:   1 : ACA Cloud Computing Exam Preparation Course - Alibaba Cloud 3   2 : Server Load Balancer - Alibaba Cloud Documentation Center 4

Server Load Balancer (SLB) is a ready-to-use service that seamlessly integrates with Elastic Compute Service (ECS) to manage varying traffic levels without manual intervention.  SLB distributes incoming traffic among multiple ECS instances according to the configured forwarding rules, increasing the service capabilities and fault tolerance of your applications 1 .  SLB supports Layer-4 (TCP/UDP) and Layer-7 (HTTP/HTTPS) load balancing, health checks, session persistence, cross-zone disaster recovery, and other advanced features 2 .

References :  1 : Alibaba Cloud Academy, “Server Load Balancer”, https://edu.alibabacloud.com/elearning/lesson/ACA-Cloud-Computing-Certification/lesson-4-server-load-balancer  2 : Alibaba Cloud, “What is Server Load Balancer?”, https://www.alibabacloud.com/help/doc-detail/27539.htm

 RDS for MySQL is a  Platform as a Service (PaaS)  product that provides a complete database solution on Alibaba Cloud. It is fully compatible with MySQL and supports various MySQL features, such as transactions, views, triggers, stored procedures, and functions. RDS for MySQL frees users from the tasks of managing the underlying operating system, runtime environment, and software packages. Users only need to focus on their business logic and data. Alibaba Cloud takes care of the database installation, configuration, backup, recovery, monitoring, scaling, and security.  References :  MySQL Database Concepts and Operations - Alibaba Cloud Academy ,  Alibaba RDS Course | Cloud Academy ,  ACA Cloud Computing Certification - Alibaba Cloud Academy

According to the Alibaba Cloud Academy, Auto Scaling is a service that automatically creates and releases ECS instances based on pre-defined rules in order to scale services to match demand. Furthermore, it can configure server load balancer and relational database service white lists, without any manual intervention. Therefore, when ECS is used with Auto Scaling, the number of ECS instances is automatically adjusted based on traffic.  References:   Introduction to Alibaba Auto Scaling - Cloud Academy ,  ACA Cloud Computing Exam Preparation Course - Alibaba Cloud , Module 4: Cloud Computing Elasticity, Lesson 1: Auto Scaling, Slide 2.

 An ECS image is a copy of data from one or more disks that are attached to an ECS instance. You cannot retrieve data directly from an ECS image and use it right away. You need to create an ECS instance from the image first, and then access the data on the disks of the instance.  References:   Elastic Compute Service:Image overview