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Why Am I Getting Charged for AWS OpenSearch When I’m Not Using It? (Bedrock Knowledge Base Warning)

I’ve been using AWS Bedrock to build chatbots and to create no-code RAG knowledge bases.

But this morning, I logged into my AWS Console and discovered a shocking surprise: my usually $20 monthly bill had skyrocketed to over $300! I’m not alone in this experience. Other AWS users have reported mysterious OpenSearch charges which highlights the same issue: AWS users are getting unexpected OpenSearch Service charges after using Bedrock Knowledge Base, even when they believe they’ve deleted everything.

Every developer’s nightmare 😅

What’s Going On?

Many AWS users have recently reported significant bill increases due to AWS OpenSearch Service, a vector database service offered by Amazon. The culprit? AWS Bedrock Knowledge Base’s default configuration.

When you create a resource with AWS Bedrock Knowledge Base, it automatically creates an OpenSearch collection – a detail that’s easy to miss but expensive to overlook.

When creating an AWS Bedrock Knowledge Base, you can quickly get started with using the default vector store, AWS OpenSearch. If you forget to delete it, then GG.

You might check your OpenSearch services in all regions and find no visible collections. However, the charges can still accumulate through Serverless Collections.

Investigating the Root Cause

Amazon OpenSearch Service -> Serverless Collections -> Set region to my default region us-east-1

Upon investigation, I discovered that my account had created SEVEN knowledge bases in one region alone!

Check ALL your commonly used resources to find the resources.

Even worse, checking the us-west-2 region revealed three more instances, each contributing to the mounting charges.

How to Prevent This From Happening

1. Be Proactive with AWS Support

While AWS support is generally responsive, they may not immediately recognize ongoing resource charges. When contacting support:

  1. Request written confirmation that resources aren’t accruing charges
  2. Ask them to monitor the situation for 24-48 hours
  3. Document any support conversations mentioning unexpected charges (this can help with refund requests)

2. Implement Robust Cost Monitoring

Set up multiple billing alerts at different thresholds. Create billing alarms with this AWS resource.

  1. Create a baseline alert (e.g., $25 for a typical $20 monthly bill)
  2. Add intermediate alerts (e.g., $50, $100)
  3. Set up a critical alert (e.g., $200) for potentially serious issues
  4. Enable AWS Cost Explorer and regularly review spending patterns

These notifications are OK, but emails are better.
If you setup your AWS Billing Alerts, you should get emails like this to notify you when your spending has gone up.

3. Establish a Resource Management Strategy

As developers, especially when working solo, we often overlook proper resource management. However, this oversight can be costly:

  • Implement regular resource audits (weekly or bi-weekly)
  • Create and maintain a resource inventory
  • Use infrastructure as code (IaC) to track resources
  • Set up automated cleanup for test/development resources

While my $300 bill was manageable, unchecked resources could easily lead to charges in the $3K or $300K. When working with cloud resources, costs can scale exponentially if left unmonitored.

For more information on AWS cost management, check out these resources: