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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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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

Pay-As-You-Go is a billing method that allows you to pay for resources after you use them. You are billed based on the actual usage of resources, such as the number of hours that an ECS instance runs or the amount of data that is transferred. Pay-As-You-Go is suitable for scenarios where the demand for resources is unpredictable, flexible, or short-term1. Pay-As-You-Go has the following advantages for the startup video streaming company:

No upfront payment: The company does not need to pay any fees in advance when they purchase ECS instances. They only pay for the resources that they actually use, which can help them save costs and optimize their cash flow1.

Flexible scaling: The company can easily scale up or down their ECS instances based on the actual demand for their service. They can add more ECS instances during peak hours or events, such as Christmas, and release them when the demand drops. They can also change the configurations of their ECS instances at any time, such as upgrading the CPU, memory, or bandwidth1.

No long-term commitment: The company does not need to commit to a long-term contract or subscription when they use Pay-As-You-Go. They can release their ECS instances at any time without incurring any penalties or fees. They can also switch to other billing methods, such as Subscription or Savings Plan, if their business needs change1.

The other billing methods of ECS are not as suitable as Pay-As-You-Go for the company’s scenario, for the following reasons:

Pay-As-You-Go with Reserved Instances: Reserved Instances are a type of discount coupon that can be used to deduct a portion of the fees incurred by Pay-As-You-Go instances that match the attributes of the Reserved Instances, such as region, zone, instance type, and operating system2. Reserved Instances require upfront payment and have a fixed term of one year or three years. They are suitable for scenarios where the demand for resources is stable and predictable, and where the user wants to enjoy lower prices than Pay-As-You-Go2. However, for the company’s scenario, Reserved Instances are not a good option, because they do not need to purchase a large number of ECS instances for a long period of time, and they want to have more flexibility and scalability in their resource management.

Subscription with Reserved Instances: Subscription is a billing method that allows you to pay for resources in advance for a specific period of time, such as one month, one year, or three years. You are billed based on the specifications and duration of the resources that you purchase, regardless of whether you use them or not. Subscription is suitable for scenarios where the demand for resources is stable and long-term, and where the user wants to enjoy lower prices than Pay-As-You-Go3. Subscription with Reserved Instances can further reduce the cost of Subscription instances by applying the Reserved Instances discounts to them2. However, for the company’s scenario, Subscription with Reserved Instances are not a good option, because they do not want to pay for resources in advance or commit to a long-term contract, and they want to have more flexibility and scalability in their resource management.

Pay-As-You-Go with Savings Plan: Savings Plan is a billing method that allows you to commit to a consistent amount of usage (measured in USD/hour) for a one-year or three-year term, and in exchange, receive a lower price for that usage4. Savings Plan can be applied to any Pay-As-You-Go instances that match the attributes of the Savings Plan, such as region, instance family, or operating system4. Savings Plan is suitable for scenarios where the demand for resources is stable and predictable, and where the user wants to enjoy lower prices than Pay-As-You-Go and more flexibility than Subscription4. However, for the company’s scenario, Savings Plan is not a good option, because they do not want to commit to a consistent amount of usage for a long period of time, and they want to have more flexibility and scalability in their resource management.

References: Pay-As-You-Go - Elastic Compute Service - Alibaba Cloud, Reserved Instances - Elastic Compute Service - Alibaba Cloud, Subscription - Elastic Compute Service - Alibaba Cloud, Savings Plan - Elastic Compute Service - Alibaba 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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Zones in the same region support low-latency intranet communication, ideal for high-availability deployments with inter-Zone fault isolation. Placement of ECS instances in the same or different Zones depends on the disaster recovery and latency needs of the application.

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ECS instance monitoring provides a process monitoring feature that allows you to check the status of specific processes, such as a Python process, and set alerts for automatic notifications if the process terminates unexpectedly. This method is quicker and more efficient than writing a custom script or manually logging in to the console.

Certificates are mandatory when using the HTTPS protocol with Alibaba Cloud SLB to secure data transmission between clients and the SLB instance. HTTPS (HTTP Secure) requires an SSL/TLS certificate to encrypt the data, ensuring secure communication over the network. For protocols like HTTP or TCP, a certificate is not required, as they do not natively support encryption.

When the black hole policy is triggered by excessive DDoS traffic, the affected server is temporarily isolated from the network to prevent further damage. During this period, no services are available, meaning the server cannot provide limited-speed services.

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.

 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.