Q. You need a fully-managed vector store for a Bedrock Knowledge Base. What is the hidden cost of OpenSearch Serverless?
A. A minimum of 2 OCUs (one indexing, one search) runs around $350 a month even with zero data or traffic. It is the right call at scale, but that idle floor makes it overkill for a small corpus.
Why? The win is matching the store to corpus size and cost shape, not picking the most powerful option.