OpenSearch Service Serverless tags does not appear in Cost Explorer

The issue you're experiencing with OpenSearch Service Serverless tags not appearing in Cost Explorer is a known concern. Even though you've added tags to your serverless collection, there are a few steps you need to take to make these tags visible and usable for cost allocation in Cost Explorer:

1. First, ensure that you have activated the cost allocation tags. To do this:

   • Sign in to the AWS Billing and Cost Management console
   • Navigate to "Cost Allocation Tags" in the sidebar
   • Find and select the tags you've applied to your OpenSearch Serverless collection
   • Click "Activate" to enable these tags for cost allocation

2. It's important to note that there can be a delay between activating cost allocation tags and seeing them appear in Cost Explorer. This process can take up to 24 hours for newly activated tags to become available.

3. Keep in mind that AWS Cost Explorer only displays tags starting from the date when you enabled user-defined cost allocation tags, not from when the resource was initially tagged. This means that even if your resources had tags for a while, Cost Explorer will show "No tag key" for all previous days until the date when the tag was enabled.

4. If you've already completed these steps and are still not seeing the tags after 24 hours, it's possible there might be an issue specific to OpenSearch Service Serverless. In this case, it would be advisable to contact AWS support for further assistance.

5. As an alternative approach, you might consider using AWS Cost and Usage Reports in combination with tools like Amazon Athena for more detailed cost breakdowns, as these can sometimes provide more granular information than Cost Explorer alone.

Remember, effective cost tracking often requires a combination of proper tagging, activation of cost allocation tags, and potentially the use of more detailed reporting tools beyond just Cost Explorer.
Sources
Tagging EMR Serverless jobs for cost tracking | AWS re:Post
How to track Amazon OpenSearch Service domain-level cost | AWS Big Data Blog
Activate cost allocation tags associated with the solution - Migration Assistant for Amazon OpenSearch Service