# Understand CloudFormation stack creation events
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During stack deployment, several events occur to create, configure, and validate the resources defined in the stack template. Understanding these events can help you optimize your stack creation process and streamline deployments.
+ **Resource creation events** – When each resource starts the creation process, a **Status** of `CREATE_IN_PROGRESS` event is set. This event indicates that the resource is being provisioned.
+ **Eventual consistency check** – A significant portion of the stack creation time is spent performing an eventual consistency check against the resources created by the stack. During this phase, the service performs internal consistency checks, ensuring the resource is fully operational and meets service stabilization criteria defined by each AWS service.
+ **Configuration complete event** – When each resource has finished the eventual consistency check phase of the provisioning, a ** Detailed status** of `CONFIGURATION_COMPLETE` event is set.
+ **Resource creation complete event** – After the resource has been created and configured as specified, and the configuration matches what is specified in the template, the **Status** of `CREATE_COMPLETE` event is set.

You can leverage the `CONFIGURATION_COMPLETE` event to streamline your stack creation process in scenarios where resource eventual consistency check is not required, such as validating a pre-production stack configuration or cross-stack provisioning. You can use this event in multiple ways. For example, you can use it as a visual signal to skip waiting for the resource or stack consistency check to finish. Or you could use it to create an automated mechanism using continuous integration and continuous delivery (CI/CD) to trigger additional actions.

**Important**  
While leveraging the `CONFIGURATION_COMPLETE` event accelerates stack creation times, you should be aware of its trade-offs. First, it's only supported for a subset of resource type that support drift detection. For a list of resource types that support drift detection, see [Resource type support](resource-import-supported-resources.md). This approach may not be suitable for all scenarios, especially where resources require thorough eventual consistency checks to ensure full operational readiness across the cloud environment (for example, in production environments). We recommend carefully assessing your deployment requirements and the criticality of the consistency checks for each resource. Use the `CONFIGURATION_COMPLETE` event to optimize deployment speeds without compromising the integrity and reliability of your infrastructure.   
Because the `CONFIGURATION_COMPLETE` event is not guaranteed to be set, any scenarios that use it should be prepared to handle a `CREATE_COMPLETE` event when no `CONFIGURATION_COMPLETE` event was set.

![\[Diagram showing the sequence of events for resource creation and eventual consistency check in a stack.\]](http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/images/configuration-complete.png)


When the stack deployment starts, both the `AWS::ECR::Repository` and `AWS::ECS::Cluster` resources start the creation process (`ResourceStatus` = `CREATE_IN_PROGRESS`. When the `AWS::ECR::Repository` resource type has started the eventual consistency check (`DetailedStatus` = `CONFIGURATION_COMPLETE`), then the `AWS::ECS::TaskDefinition` resource can start the creation process. Similarly, once the `AWS::ECS::TaskDefinition` resource begins the eventual consistency check, the `AWS::ECS::Service` resource start the creation process.

**`CREATE_IN_PROGRESS` and `CREATE_COMPLETE` events**
+ **[Stack]:** `CREATE_IN_PROGRESS`
+ **[Resource]:** ECR Repository `CREATE_IN_PROGRESS`
+ **[Resource]:** ECS Cluster `CREATE_IN_PROGRESS`
+ **[Resource]:** ECR Repository `CREATE_IN_PROGRESS`, `CONFIGURATION_COMPLETE`
+ **[Resource]:** ECS Task Definition `CREATE_IN_PROGRESS`
+ **[Resource]:** ECS Cluster `CREATE_IN_PROGRESS`, `CONFIGURATION_COMPLETE`
+ **[Resource]:** ECS Task Definition `CREATE_IN_PROGRESS`, `CONFIGURATION_COMPLETE`
+ **[Resource]:** ECS Service `CREATE_IN_PROGRESS`
+ **[Resource]:** ECR Repository `CREATE_COMPLETE`
+ **[Resource]:** ECS Cluster `CREATE_COMPLETE`
+ **[Resource]:** ECS Service `CREATE_IN_PROGRESS`, `CONFIGURATION_COMPLETE`
+ **[Stack]:** `CREATE_IN_PROGRESS`, `CONFIGURATION_COMPLETE`
+ **[Resource]:** ECS Task Definition `CREATE_COMPLETE`
+ **[Resource]:** ECS Service `CREATE_COMPLETE`
+ **[Stack]:** `CREATE_COMPLETE`