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Auto Scaling

Best Practices

Reducing costs by using spot instances

Auto Scaling allows you to add Pay-as-you-go and spot instances to the same scaling group at the same time, helping you reduce costs while responding to business fluctuations. This topic describes how to build a low-cost, highly efficient scaling task that can respond to business surges at any time.

What is a spot instance?

Spot Instance is a unique Pay-as-you-go method. Compared with standard Pay-as-you-go, the compute resources for spot instances can be purchased with a certain discount. The price changes in real time with market demand and supply. When you purchase a spot instance, you need to set the maximum price you are willing to pay for the instance. It only represents your purchasing intention. The settlement is still based on the market price.

ECS instances purchased with this billing method have the same performance as regular servers. However, when the inventory is insufficient, or the market price exceeds the maximum price you set, the system will automatically release instance resources and reclaim the discounted ECS instances. For the reclaim mechanism, please refer to Reclaiming spot instances. The price you set must be between the current spot market price and the Pay-as-you-go instance price. The higher your bid, the greater the chance of purchasing or retaining the spot instance.

For the operation process of spot instances, see the following figure. For more information, see Operation process.

Application scenarios for spot instances

The operation and release of spot instances are subject to resource inventory and market price fluctuations. Spot instances are more applicable to stateless application scenarios. Typical use cases include stateless web services, image rendering, big data analytics, offline analytics, and large-scale parallel computing and testing workloads. The greater an application's distributed nature, scalability, and fault tolerance, the more effectively it can use spot instances to reduce costs and boost throughput.

warning

To avoid impacts on business operations by the interrupt reclamation mechanism, do not use spot instances for long-term workloads or stateful applications with high stability requirements, such as databases. Preserving application state is challenging when a spot instance is released.

Application of spot instances in Auto Scaling

Compared with traditional Pay-as-you-go instances, spot instances integrated with Auto Scaling deliver significant cost savings. However, due to their instability, there may be cases where instance scale-out fails or instances are automatically released, which can affect business operations. Evaluate and use them appropriately based on your actual needs. The following items outline recommended solutions to help you optimize cost efficiency while maximizing business operational stability.

Ensure stable operation of core business

Specify the minimum Pay-as-you-go instance count or capacity or the percentage of Pay-as-you-go instances in a scaling group to fix the number of Pay-as-you-go instances in the scaling group. Scale out or in spot instances on the premise of maintaining stable operation of core business.

Improve the scale-out success rate

Configure multiple instance types: Select several instance types with similar performance and pricing in the launch template or scaling configuration. During scale-out activities, if the higher-priority instance type is out of stock or fails to be used to create instances, the system automatically uses lower-priority types to create instances.

Configure multiple subnets: Select multiple subnets where instances can be deployed. During scale-out activities, spot instances can be created based on inventory availability across multiple availability zones.

Enable Pay-as-you-go instances as a supplement for spot instances: Create Pay-as-you-go instances of the same type when spot instances are out of stock.

Reduce the impact of instance reclaim on business

Enable spot instance replacement upon expiration: Enable new spot instances to be automatically created to replace existing ones approximately 5 minutes before the original spot instances are reclaimed. This prevents business performance degradation caused by unexpected spot instance reclaim.

Procedure

This section describes the configuration methods for applying spot instances in Auto Scaling.

Configure multiple subnets: In the "Basic Information" section, click the "Modify Subnet" button, select multiple subnets, and click the "Confirm" button. Learn more.

Configure multiple instance types: In the "Basic Information" section, click the "Add scaling configuration source" or "Modify scaling configuration source" button to modify the scaling configuration or launch template already associated with the scaling group.

Click the "Change scaling configuration" or "Modify the Launch Template" button on the right side of the scaling configuration source.

Select "Spot" for "Billing method".

Select "Enable multi-type selection" or "Extended Launch Template Configuration", select multiple instance types, and drag the types to sort them.

Select the price mode for spot instances.

Spot strategy	Description	Purchase result
Set maximum price	You need to set a maximum price for the target instance. The maximum price only represents your purchasing intent, and the settlement is based on market price. This price must be between the current spot market price and the pay-as-you-go instance price. The higher your bid, the greater the chance of purchasing or retaining the spot instance. By clicking "View historical prices", you can view historical prices.	If the bid price is greater than or equal to the market price and inventory is sufficient, spot instances are purchased as expected. If the bid price is less than the market price or inventory is insufficient, spot instance purchase fails.
Automatic bid	The system automatically uses the Pay-as-you-go instance price as the maximum bid price (indicating purchase intent only). This means the real-time market price is consistently used as the billing and settlement price for spot instances. If inventory is insufficient, the instances will be automatically released.	Purchase succeeds due to sufficient stock.
Automatic bid			Purchase fails due to insufficient stock.

Click the "OK" button.

Configure the scaling policy: In the "Policy information" section, click the "Configure policy" button, turn on "Advanced settings", configure parameters as described in the following table, and then click "Save". Learn more.

Parameter	Description	Example
Minimum Pay-as-you-go Instances/Capacity	The minimum Pay-as-you-go instance count or capacity in the scaling group. When the Pay-as-you-go instance count or capacity in the scaling group is less than the value of this parameter, Pay-as-you-go instances will be created first.	2
Percentage of pay-as-you-go Instances	The proportion of Pay-as-you-go instances in the scaling group. When the percentage is calculated, the Pay-as-you-go instances corresponding to the minimum Pay-as-you-go instance count or capacity in the group are not included.	50%
Spot Replacement Before Expiration	If you select "Enable", about 5 minutes before a spot instance is reclaimed, the scaling group will proactively create a new spot instance to replace the current spot instance.	Enable
Use Pay-as-you-go Instances Supplement Spot Instances	When the automatic scale-out policy is met, if spot instances are sold out, Pay-as-you-go instances of the same instance type will be created to meet the scale-out demand.	Enable

Example: With the above configuration, when the scaling group automatically scales out by 10 instances:

If the spot instance bid price is greater than or equal to the market price and inventory is sufficient, 6 Pay-as-you-go instances (calculation: 2 + 8 × 50% = 6) and 4 spot instances (calculation: 8 × 50% = 4) will be created.

If the spot instance bid price is greater than or equal to the market price and only 2 instances are left in inventory, Pay-as-you-go instances will be used to supplement spot instances. Specifically, 8 Pay-as-you-go instances and 2 spot instances will be created.

Configure spot instance scaling notification

The platform can send notifications via in-site messages, email, SMS, alert callbacks, and other channels to help you promptly track spot instance scaling changes.

Enable scaling notification capabilities for the scaling group to monitor instance scaling activities within the group.

Subscribe to event notifications to receive advance alerts about upcoming instance releases through in-site messages, SMS, email, or other channels 5 minutes before spot instance release.

View spot instance events via the console, instance metadata, or API.

Last updated: 2026.06.24 17:08:56