Alibaba Cloud ACP-Cloud1 ACP Cloud Computing Certification Exam Practice Test

Latency on an RDS read-only instance can be caused by high loads on the instance itself, inadequate instance specifications, or excessive write operations on the master instance, as these factors directly impact replication delay and resource contention. However, a high load on the ECS instance connected to the RDS read-only instance would not inherently cause latency on the RDS instance, as the ECS and RDS operate independently in terms of processing.

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Alibaba Cloud SLB allows users to select between private and public SLB based on business needs. A public SLB provides a public IP address for Internet-facing applications, while a private SLB provides a private IP address for internal applications within a VPC. Alibaba Cloud assigns the appropriate IP type automatically based on the user’s selection of SLB type.

According to the Alibaba Cloud Academy, Auto Scaling supports three scaling modes: manual mode, scheduled task, and cloud monitor and event-triggered task. Manual mode requires manual intervention to adjust the number of ECS instances, which is not feasible and with minimum operation efforts. Scheduled task allows you to set the time and number of ECS instances to be added or removed in advance, which is suitable for predictable traffic changes. Cloud monitor and event-triggered task allows you to set the monitoring metrics and thresholds for scaling actions, which is suitable for dynamic traffic changes. Healthy check mode is not a scaling mode, but a feature of SLB to ensure the availability of ECS instances behind the load balancer. References: : ACP Cloud Computing Certification Preparation Course - Auto Scaling, : ACP Cloud Computing Certification Preparation Course - Server Load Balancer

In Alibaba Cloud SLB, Layer-7 (HTTP/HTTPS) services require enabling the "X-Forwarded-For" header to retrieve the real IP address of clients, while Layer-4 (TCP/UDP) services can obtain the real IP address directly without additional settings.

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 When the scheduled task is activated once, 4 ECS instances will be added in the scaling group. This is because the scaling rule “Add 6 ECS instances” will increase the number of instances in the scaling group to 9, which exceeds the maximum number of instances (7) that is set for the scaling group. Therefore, Auto Scaling will only add 4 ECS instances to reach the maximum number of instances. The remaining 2 ECS instances will not be added to avoid exceeding the quota. 

Data Transmission Service (DTS) is a real-time data streaming service that supports data transmission between data sources such as relational databases, NoSQL, and Big Data (OLAP). DTS supports data migration, data synchronization, and change data subscription scenarios. DTS can migrate your data to and from most of the widely used commercial and open source databases. It supports homogeneous migrations such as MySQL to MySQL, as well as heterogeneous migrations between different database platforms, such as Oracle to MySQL. Migrations can be from on-premises databases to RDS or ECS, databases running on ECS to RDS, or vice versa, as well as from one RDS database to another RDS database. DTS also supports database schema replication between instances, which means that DTS can automatically create the same schema as the source database in the target database. DTS also supports warning when source and destination has some unresolved conflict found, such as data type mismatch, primary key conflict, or foreign key constraint violation. DTS can help you resolve these conflicts by providing suggestions or allowing you to modify the data mapping rules. Therefore, the correct answer is C. Supports all of the above functions. References:

1: Data Transmission Service - Alibaba Cloud

2: What is Data Transmission Service? - Alibaba Cloud

3: Database Migration - AlibabaCloud

4: Cloud Migration without Stopping Services: Alibaba Cloud DTS

 PPPoE stands for Point-to-Point Protocol over Ethernet, which is a network protocol that encapsulates PPP frames in Ethernet frames and allows multiple computers to share a single Internet connection. PPPoE is typically used by Internet service providers (ISPs) to provide broadband access to their customers, such as DSL or cable modem. PPPoE is not a protocol that is commonly supported by Open API for cloud computing service providers, because it is not designed for web-based communication and requires a dedicated connection between the client and the server. Open API, on the other hand, is a term that refers to a set of publicly available application programming interfaces (APIs) that allow developers to access the functionality and data of cloud computing service providers. Open API usually follows standard protocols that are widely used on the web, such as HTTP, Restful, and Web Service. HTTP stands for Hypertext Transfer Protocol, which is the foundation of data communication on the web. HTTP defines how messages are formatted and transmitted, and what actions web servers and browsers should take in response to various commands. HTTP is a stateless protocol, which means that each request is independent and does not depend on any previous requests or responses. Restful stands for Representational State Transfer, which is an architectural style for designing web services that are based on the concept of resources. Restful web services use HTTP methods (such as GET, POST, PUT, and DELETE) to perform operations on resources, and use standard formats (such as JSON or XML) to exchange data. Restful web services are stateless, scalable, and cacheable, and aim to provide a uniform interface for interacting with different types of resources. Web Service is a generic term that refers to any software service that is available over the web and uses a standardized format for communication, such as SOAP or REST. Web Service allows different applications to communicate and exchange data across different platforms and languages. Web Service can be described using a specification language, such as WSDL or OpenAPI, which defines the structure, operations, and parameters of the service. Web Service can also be registered and discovered using a directory service, such as UDDI or Swagger.

According to the Alibaba Cloud Elastic Compute Service documentation, if the current public bandwidth does not meet your business requirements, you can upgrade or downgrade the public bandwidth configurations without the need to reboot the ECS instance. This can improve the network performance and response speed of the ECS instance. Upgrading the CPU, memory, or disk of the ECS instance may not solve the issue of bandwidth utilization, and may require rebooting the ECS instance. References: Public bandwidth - Elastic Compute Service

Alibaba Cloud Object Storage Service (OSS) is ideal for storing large amounts of unstructured data, such as images and videos. By migrating static files to OSS, you can free up disk space on your ECS instance, allowing you to efficiently handle storage needs as your business scales. OSS is a highly scalable and cost-effective solution for handling media files and other static assets.

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A low CDN cache hit rate can be due to low website traffic, poor cache configurations (such as a short Cache Expiry Time), or the presence of dynamic resources that require frequent retrieval from the origin. Proper configuration of "Cache-Control" and "Expires" headers is necessary to ensure caching.

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Before data communication is set up, the security groups match the security group rules one by one to query whether to allow access requests. If the protocol type, port range, authorization type, and authorization object of two security group rules are the same, the following rules apply:

If the two rules have the same priority, the rule of the denial policy takes effect first, and the rule of the allowed policy does not take effect. This is because the security group rules follow the principle of minimum permission, which means that the most restrictive rule is applied when there is a conflict.

If the two rules have different priorities, the rule with a smaller priority number takes effect. This is because the security group rules follow the principle of priority, which means that the rule with a higher priority (lower number) is applied when there is a conflict. References: ECS Security Groups - Alibaba Fundamentals - Cloud Academy, Security group rules - Elastic Compute Service - Alibaba Cloud Documentation Center

A. Management and maintenance: To prevent emergent service termination, users need to know the underlying detail like how the data is archived in the resource pool. This is incorrect because cloud storage is designed to abstract the underlying details of how the data is stored and managed from the users. Users do not need to worry about the hardware, software, or network issues that may affect the data availability or reliability. The cloud storage provider is responsible for maintaining and managing the storage infrastructure and ensuring the service continuity1.

B. Service on demand Cloud storage has a huge resources pool, users can apply for and use the resources on demand. This is correct because cloud storage is based on the cloud computing model of service on demand, which means that users can request and access the storage resources as needed, without having to purchase or provision them in advance. Cloud storage providers offer flexible pricing models that allow users to pay only for the storage they use2.

C. High reliability and availability: Provides very high reliability and availability through technologies like 3 redundant copies, automatic failure recovery, etc. This is correct because cloud storage uses various technologies and methods to ensure that the data stored in the cloud is always accessible and durable. For example, cloud storage providers typically replicate the data across multiple servers, regions, or zones to prevent data loss due to hardware failure, natural disaster, or human error. Cloud storage providers also use automatic failure recovery mechanisms to detect and repair any issues that may affect the data integrity or availability3.

D. Ultra-large scale: Data storage can reach TB or even PB level. This is correct because cloud storage can handle massive amounts of data, ranging from terabytes (TB) to petabytes (PB) or even exabytes (EB). Cloud storage providers have the infrastructure and expertise to scale up the storage capacity and performance to meet the growing data needs of users. Cloud storage can support various types of data, such as structured, unstructured, or semi-structured data, and various use cases, such as data backup, data archiving, data analytics, or data sharing.

E. Transparent service: Provides the service through a single SDK. This is incorrect because cloud storage is not a transparent service, but a service that requires users to interact with it through a specific interface or protocol. Cloud storage providers usually offer different types of storage services, such as object storage, block storage, or file storage, each with its own characteristics and features. Users need to choose the appropriate storage service for their data and use the corresponding software development kit (SDK), application programming interface (API), or command-line interface (CLI) to access and manipulate the data.

F. High scalability Storage capacity can be dynamically scaled to meet the needs. This is correct because cloud storage is highly scalable, meaning that users can increase or decrease the storage capacity according to their data needs. Cloud storage providers offer elastic storage services that can automatically adjust the storage resources based on the demand, without requiring users to manually provision or deprovision them. Cloud storage also allows users to scale the storage performance, such as throughput, latency, or bandwidth, to optimize the data access and transfer.

References: 1: What is Cloud Storage? - Cloud Storage Explained - AWS 2: What is Cloud Storage & How Does it Work? | Google Cloud 3: Cloud Storage Reliability and Availability | Cloud Storage Documentation : What is Cloud Storage? - Definition from Techopedia : Cloud Storage Types: Object, Block, and File | IBM : Cloud Storage Scalability | Cloud Storage Documentation

In Alibaba Cloud RDS, multiple databases can be created within a single instance, allowing users to manage different databases under one RDS instance efficiently. However, databases within the same instance must have unique names, and resources such as CPU and memory are shared across databases within the same instance, contrary to the options provided in answers B and C.

To prevent frequent alerts when User A logs in from Shanghai, the best solution is to configure the Security Center to recognize Shanghai as a frequent login location. This will prevent unnecessary security alerts each time User A accesses the server from this location.

Alibaba Cloud Auto Scaling ensures transaction completeness during scaling activities. If the intended number of ECS instances cannot be added to the scaling group, Auto Scaling rolls back the entire activity, releasing any partially added instances. This behavior prevents incomplete scaling activities, ensuring the scaling action either fully succeeds or is reverted entirely.

For optimal use of SLB with Auto Scaling, enabling Health Check is essential to determine which instances are healthy and ready to handle traffic. SLB doesn’t require all backend servers to have the same OS, be in the same scaling group, or have identical configurations, as it can manage heterogeneous server setups within the same load-balancing group.

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Alibaba Cloud OSS automatically maintains three copies of each data object to ensure data reliability and redundancy. This setup allows OSS to recover data automatically without human intervention in case of hardware or system failures, ensuring high data durability.

 To manually install Alibaba Cloud Security Center on the server, you need to have the system administrator privilege. This is because the Security Center agent requires access to the system files and processes, and can perform security operations such as vulnerability scanning, intrusion detection, and threat blocking. A common user privilege or a database access privilege is not sufficient to install the Security Center agent. An FTP service privilege is irrelevant to the installation process. 

Alibaba Cloud provides comprehensive security protection covering networks, hosts, applications, databases, and content for on-cloud clients, but users still need to pay attention to security protection issues. Alibaba Cloud and its customers are jointly responsible for the security of customers’ applications built on Alibaba Cloud. With security responsibilities shared between Alibaba Cloud and its customers, Alibaba Cloud provides a secure infrastructure to decrease the enterprise security burden of customers. As such, customers can configure and use cloud products in a secure manner, thus relieving much of the underlying security burdens while allowing customers to focus more on their core business needs. However, customers still need to follow the best practices and guidelines for cloud security, such as using strong passwords, enabling multi-factor authentication, encrypting sensitive data, applying security patches, etc. Customers also need to monitor and manage the security risks and incidents of their cloud environment using Alibaba Cloud’s security products and services, such as Security Center, ActionTrail, Cloud Firewall, etc. References: Cloud Security- Alibaba Cloud, Security & Compliance Center, Shared Responsibility

There is no limit on the number of objects that can be stored in a single OSS bucket in Alibaba Cloud. OSS is designed to support massive data storage, allowing users to store an unlimited number of files within a bucket. The only limitations are the bucket storage capacity and account-level quotas.

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For a service focused on storing and providing fast access to a massive amount of images, the team should use:

Object Storage Service (OSS): For scalable and cost-effective storage of large image datasets.

Elastic Compute Service (ECS): For running the application’s backend and API logic.

Content Delivery Network (CDN): To cache and accelerate image delivery globally, improving access speed for users worldwide.While Auto Scaling is useful for applications with highly variable compute demands, it is not essential for this setup based on the described requirements.

 Auto Scaling is a service that automatically adjusts the number of ECS instances based on your business needs and policies. You can use Auto Scaling to cope with unpredictable or periodic workloads. Auto Scaling supports three scaling modes: scheduled, dynamic, and fixed1. Dynamic scaling mode allows you to automatically add or remove ECS instances based on CloudMonitor metrics, such as CPU utilization, memory utilization, inbound traffic, and outbound traffic2. You can configure scaling rules and scaling policies to define the conditions and actions for dynamic scaling. For example, you can set a scaling rule to add one ECS instance when the average CPU utilization of the scaling group exceeds 80% for five consecutive minutes3. Dynamic scaling mode is suitable for scenarios where you cannot predict service changes or do not have enough historical data to set a schedule4. References:

1: Auto Scaling overview - Auto Scaling - Alibaba Cloud Documentation Center1

2: Scaling modes - Auto Scaling - Alibaba Cloud Documentation Center2

3: Create a scaling rule - Auto Scaling - Alibaba Cloud Documentation Center3

4: Auto Scaling: Automatically Adjusts Computing Resources - Alibaba Cloud5

The port 3306 is the default port on which MySQL is usually configured. This port is used by MySQL clients and applications to connect to the MySQL server. If you are using any other port, you should allow traffic to that specific port instead. Alibaba Cloud RDS for MySQL also uses this port by default, unless you specify a different port when creating the RDS instance. You can view and modify the port number of your RDS instance in the RDS console. References: How to configure an Amazon RDS environment for MySQL, Connecting to a DB instance running the MySQL database engine, [Create an ApsaraDB RDS for MySQL instance]

When using Alibaba Cloud SLB, you can set different weights for backend ECS instances. The higher the weight of a backend ECS instance, the more load will be assigned to it. However, the load distribution is not based on the absolute value of the weight, but on the proportion of the weight in the total weight of all healthy backend ECS instances. For example, if there are two healthy backend ECS instances with weights of 100 and 200 respectively, the first instance will receive 33.3% of the load, and the second instance will receive 66.7% of the load. Therefore, to determine the load distribution of the 5 ECS instances in the question, we need to know the weight settings of the remaining 4 ECS instances. Without this information, we cannot tell what would happen. The other options are incorrect because they are based on wrong assumptions or misunderstandings of the SLB weight setting mechanism. 

Cloud computing is characterized by large-scale infrastructure, high availability, on-demand service provisioning, and versatility in handling diverse applications and workloads. It supports both multi-tenant and single-tenant configurations, and although containerization is popular, cloud computing is not limited to container-based architectures.

Alibaba Cloud OSS ensures high reliability and availability by maintaining multiple copies of data across different physical locations, allowing it to recover within minutes in the event of hardware failures. This redundancy mechanism provides strong data durability and service continuity.

Public cloud computing offers advantages such as rapid deployment, increased flexibility and scalability, reduced costs associated with infrastructure, and minimized management and maintenance efforts. Option E is incorrect, as cloud providers typically manage the underlying infrastructure, and users do not have full control over it. Cloud computing abstracts the infrastructure layer, allowing users to focus on applications without needing to manage physical resources.

To isolate ECS instances within different VSwitches in a VPC while allowing them to access the internet and other intranet resources, each VSwitch's instances should be in separate Security Groups. By configuring each group to allow all VPC CIDR blocks first and then restricting access to other VSwitch CIDR blocks with a higher priority rule, instances in each VSwitch are isolated without affecting the VPC's external connections. This approach follows Alibaba Cloud's Security Group best practices and CIDR-based access control within VPC environments.

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OSS does not use a hierarchical structure for objects, but instead uses a flat structure. All elements are stored as objects in buckets. To use OSS in the same manner in which local file systems are used, you can configure Cloud Storage Gateway (CSG).

https://www.alibabacloud.c om/help/doc-detail/31817.htm

 The statement C is correct, because in an OSS bucket, all elements are stored as objects. An object is the basic unit of OSS storage. Each object consists of a unique key, data, and metadata. The key is the name of the object, which is used to identify the object in a bucket. The data is the content of the object, which can be any type of file, such as text, image, video, or audio. The metadata is the information about the object, such as its size, type, creation time, and custom attributes. References: = Object Storage Service:Overview - Alibaba Cloud

The X-Forwarded-For field in HTTP header is used to identify the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When the “Obtain the Visitor’s Real IP Address” function is enabled in Alibaba Cloud SLB, the SLB instance adds the X-Forwarded-For field to the HTTP header of each request and forwards the request to the backend server. The backend server can then obtain the real IP address of the visitor from the X-Forwarded-For field1. The format of the X-Forwarded-For field is as follows:

X-Forwarded-For: client, proxy1, proxy2

where the value is a comma+space separated list of IP addresses, the left-most being the original client, and each successive proxy that passed the request adding the IP address where it received the request from. In this example, the request passed through proxy1, proxy2, and then the SLB instance (proxy3).2

References: Obtain client IP addresses - Server Load Balancer - Alibaba Cloud, X-Forwarded-For - MDN Web Docs

The ossbrowser is a graphical tool provided by Alibaba Cloud for uploading and downloading files in OSS, offering an intuitive interface for managing objects. Other tools like ossutil and osscmd are command-line tools, while ossfs is used to mount OSS as a file system on Linux, not a graphical tool.

Objects cannot be directly renamed in OSS. To rename an object in the bucket, you can copy the source object to the destination object and delete the source object. This is because the object name is part of the object URL and cannot be changed without affecting the access to the object. However, if you enable the hierarchical namespace feature for a bucket, you can rename objects in the bucket by using the OSS console or SDKs. References:

Object Storage Service:Rename objects - Alibaba Cloud

Object Storage Service:Rename objects - Alibaba Cloud

Recipe OSS: How to rename an object? (Alibaba Cloud)

Alibaba Cloud RDS automatically deploys instances in master-slave mode (high availability) without additional configuration or charges. This ensures data redundancy and disaster recovery by maintaining synchronous data replication from the master to the slave instance.

SQL injection attacks primarily target databases by exploiting vulnerabilities in web applications. Attackers manipulate SQL queries to gain unauthorized access to the application's backend database, which may lead to data leakage or destruction. Although SQL injection affects the data stored in databases and not directly files or images on the server, the primary target remains the application layer through which the attack is conducted.

In Alibaba Cloud RDS, both the master and read-only instances must reside within the same region. Cross-region replication for RDS read-only instances is not supported, as RDS read replicas are designed for high availability and load balancing within a single region.

Alibaba Cloud Elastic Compute Service (ECS) instances in different security groups are isolated from each other by default, but they can communicate with each other if the security group rules allow it. A security group is a virtual firewall that controls the inbound and outbound traffic of ECS instances. You can configure security group rules to specify which IP addresses, protocols, and ports can access the ECS instances in a security group. You can also authorize other security groups to access the ECS instances in a security group, which enables cross-security group communication. References: Manage ECS instances in security groups, Security FAQ, ECS Security Groups - Alibaba Fundamentals

 You can change the private IP address of an ECS instance after it is created, but you need to stop the instance first. The private IP address must be within the CIDR block of the VPC and the VSwitch that the instance belongs to. You can modify the private IP address of an instance by using the console or the API. References: 3, ACP Cloud Computing Certification - Alibaba Cloud Academy

After stopping an Alibaba Cloud Elastic Compute Service (ECS) instance, you will still be charged for some resources related to that ECS instance, such as disks, snapshots, and public IP addresses, until you release them. The charging policy depends on the billing method and network type of the ECS instance. For pay-as-you-go instances, you can choose whether to enable the No fees for stopped instances feature, which allows you to stop paying for vCPUs and memory when the instance is stopped. However, this feature is only available for VPC-connected instances in some regions1. For subscription instances, you will be charged for the entire subscription period regardless of whether the instance is running or stopped2. References:

1: Billing FAQ - Elastic Compute Service - Alibaba Cloud Documentation Center1

2: Billing overview - Elastic Compute Service - Alibaba Cloud Documentation Center2

Intelligent DNS resolution is a feature of Alibaba Cloud DNS that allows users to configure different IP addresses for the same domain name based on the geographic locations or ISPs of the visitors. This way, visitors can access the nearest or optimal server for better performance and availability. Intelligent DNS resolution does not support web page content caching, which is a function of Alibaba Cloud CDN. Alibaba Cloud CDN is a distributed network that delivers content from the origin server to the edge nodes closest to the end users, reducing the network latency and bandwidth consumption. Alibaba Cloud CDN caches the static content of the web pages, such as images, CSS, and JavaScript files, on the edge nodes, so that the users can access them faster and reduce the load on the origin server. A user will receive data from the cache in the first-time access, and then will be updated from the origin site in subsequent requests based on the cache expiration time.

References:

1: Intelligent DNS resolution - Alibaba Cloud DNS - Alibaba Cloud Documentation Center

4: Alibaba Cloud Content Delivery Network (CDN) performs content acceleration with the support of intelligent DNS resolution The following function_________is NOT included in intelligent DNS resolution.

5: Alibaba Cloud DNS:Alibaba Cloud line for intelligent DNS resolution (September 16, 2020) - Alibaba Cloud Documentation Center

Alibaba Cloud SLB can distribute user requests to backend ECS instances, but these ECS instances do not have to have the same specification (CPU, Memory). SLB virtualizes the added group of ECS instances in the same region into an application pool, and you can manage backend servers through either the default server group, a primary server group, or VServer groups. You can add ECS instances of different specifications to the same server group or VServer group according to your needs. SLB supports weighted round-robin (WRR) and weighted least connections (WLC) algorithms to balance the load among backend servers with different weights. References:

SLB overview - Alibaba Cloud

Backend server overview - Alibaba Cloud

What is Server Load Balancer and How It Works - Alibaba Cloud

Server Load Balancer - Alibaba Cloud

Alibaba Server Load Balancer (SLB) Course - Cloud Academy

When using Auto Scaling with Server Load Balancer (SLB), both the scaling group and the SLB instance must reside in the same region. This is because region-specific configurations enable low-latency connections and proper integration between the resources, ensuring the scaling group can register with the SLB instance effectively.

To improve access speeds for U.S. users, Company G can enable OSS with CDN in the West US (Silicon Valley) region. By deploying CDN in a region close to the target audience, the static content stored in OSS can be cached and delivered more efficiently. CDN caches the content at edge locations, reducing latency for users in different geographical areas. This approach is ideal for expanding the application to international markets while maintaining fast access times.

In Alibaba Cloud RDS, read-only instances are synchronized from the master instance but do not allow actions such as creating or deleting databases, configuring backup policies, or changing account authorizations. However, you can configure the read-only instance’s whitelist to control access.

RDS accounts can be used to connect with the databases created on a given RDS instance. Each account can be bound with multiple databases. However, the read/write permissions of each database can be assigned to multiple RDS accounts, not just one. For example, you can create an account with read-only permission for all databases, and another account with read-write permission for a specific database. This way, you can manage the access control of your databases more flexibly and securely. References:  Introduction to ApsaraDB RDS - Alibaba Cloud Document Center - User Management - Account Permissions

After stopping an Alibaba Cloud Elastic Compute Service (ECS) instance, you will not be charged for the instance usage fee or the public bandwidth fee (if applicable) until you start the instance again. However, you will still be charged for the disk usage fee and the snapshot usage fee (if applicable) regardless of which region the instance is located in. This is because the disks and snapshots are still occupying the storage space and need to be billed accordingly. Therefore, the statement is false. References: 1 - Billing FAQ - Alibaba Cloud Document Center - What fees do I need to pay after I stop a Pay-As-You-Go instance?

Alibaba Cloud Content Delivery Network (CDN) is a distributed network that delivers content to users based on their geographic locations. CDN can reduce the latency and improve the user experience of accessing content from the Internet. CDN can also reduce the Internet downstream traffic of OSS by caching the content in the edge nodes of CDN. The Internet traffic cost of CDN is lower than that of OSS, and the back-to-source traffic cost from CDN to OSS is also lower than a user access to OSS directly. Therefore, using CDN can reduce the traffic cost of OSS. References: Object Storage Service (OSS) - Alibaba Cloud, Storage Services Overview:OSS - Alibaba Cloud, Introduction to Object Storage Service - Alibaba Cloud, Object Storage Service(OSS): Store Data Safely In The Cloud

For Layer-4 SLB using TCP, the health check determines ECS instance availability based on the successful completion of a TCP 3-way handshake. This ensures that the backend server is reachable and can accept connections, which is critical for reliable TCP-based load balancing.

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A route table is a set of rules that determine how network traffic is routed within a VPC or between different network instances1. A VRouter is a hub that connects all VSwitches in the same VPC and enables communication between them2. When you create a VPC, a VRouter and a default route table are automatically created for the VPC1. The default route table contains system routes that are automatically generated by the system based on the network topology1. The system routes cannot be modified or deleted1.

However, you can also create custom route tables for your VPC and add custom routes to them1. Custom routes are manually configured by users to route traffic to specific destinations, such as other VPCs, VBRs, VPN Gateways, or NAT Gateways1. Custom routes can be modified or deleted as needed1. You can also associate VSwitches with different route tables to implement fine-grained routing control1.

Therefore, the statement that the routing entries of the route table can not be modified manually is not correct, as it only applies to system routes, not custom routes. The other statements are correct, as each VRouter may have multiple route tables, one default and several custom1; when a VPC is deleted, the corresponding route table is also deleted3; and the default route table cannot be deleted1. References: Route table overview - Virtual Private Cloud - Alibaba Cloud Documentation Center, VRouter overview - Virtual Private Cloud - Alibaba Cloud Documentation Center, Delete a VPC - Virtual Private Cloud - Alibaba Cloud Documentation Center

Alibaba Cloud CDN is particularly effective for websites with high traffic and static resources that are frequently accessed by different users. In such cases, CDN caching and delivery from edge nodes greatly reduce the load on origin servers and improve access speed for end users, especially in regions closer to the edge nodes.

Alibaba Cloud OSS is designed for scalable and secure object storage, allowing users to upload and download files through multiple interfaces, including the web console and APIs, offering flexibility and ease of use for developers and administrators.

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Security Groups in Alibaba Cloud are VPC-specific. They can only include ECS instances within the same VPC, but they are not restricted to a single zone within the region. This means a Security Group can manage access rules across multiple ECS instances in the same VPC, regardless of the specific zone they are in, as long as they are within the same region. This ensures VPC security compliance across zones in the same region.

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This statement is not correct because it is not a good practice to store user access information on each ECS instance in the scaling group. This is because the ECS instances are dynamic and can be added or removed by the Auto Scaling service based on the load and demand. Therefore, the data stored on the ECS instances may be lost or inconsistent if the instances are terminated or replaced. Moreover, this approach does not provide a centralized and unified way to access and analyze the data, which may affect the accuracy and efficiency of the analysis. Therefore, it is better to use other services such as ApsaraDB for RDS, ApsaraDB for Memcache, or OSS to store the user access information in a persistent and scalable manner. References: Auto Scaling, ApsaraDB for RDS, ApsaraDB for Memcache, OSS

The maximum number of connections to an RDS instance primarily depends on the memory size of the instance. Higher memory capacity allows for more simultaneous connections, as memory is a key resource in managing and maintaining connections. Alibaba Cloud RDS scales the connection limit based on the instance's memory allocation to ensure stable database performance.