OpenSearch Reserved Instances - Purchased but not showing

Thank you for your question, Richard. I understand your concern about the Reserved Instances (RIs) you've purchased for OpenSearch not showing immediate effects on your billing or recommendations. Let me clarify a few points for you.

First, it's important to note that Reserved Instances are essentially a billing discount applied to On-Demand Instances in your account. The instances themselves are identical to On-Demand Instances, but you receive a discounted rate for committing to a long-term usage.

Since you purchased the RIs with a "No Upfront" option for a 3-year term, you won't see an immediate large charge. Instead, you'll be billed at a discounted hourly rate for the duration of the term. This discounted rate will be applied automatically to matching instances in your account.

Regarding the billing effect, it may take some time for the changes to reflect in your billing dashboard. AWS typically updates billing information periodically, so you might not see the impact immediately. Give it a few days, and you should start seeing the discounted rates applied to your eligible instances.

As for the recommendation to purchase these instances still showing on your dashboard, this could be due to a delay in updating the recommendations. AWS systems may take some time to process your recent purchase and update the recommendations accordingly. This delay doesn't necessarily mean there's an issue with your purchase.

You don't need to manually associate the Reserved Instances with your account. AWS automatically applies the RI discount to eligible running instances in your account. As long as you have matching instances running (same instance type, region, and tenancy), the discount will be applied automatically.

Given that you can see the purchased RIs in your Reserved Instance leases list, and they're showing as active with the correct instance type and region, it appears that you've made the correct purchase. The r5.4xlarge.search and c5.4xlarge.search instance types are valid for OpenSearch Service.

If you continue to have concerns or don't see any changes in your billing after a few days, it would be advisable to contact AWS Support. They can provide a detailed review of your account and confirm that everything is set up correctly.

Remember, RIs are a long-term commitment, and the benefits will be realized over the course of the 3-year term you've selected. Keep monitoring your billing over the next few weeks, and you should start to see the cost savings reflected in your account.
Sources
Reserved Instances in Amazon OpenSearch Service - Amazon OpenSearch Service
OpenSearch, instances vs. nodes | AWS re:Post