RAG on a Budget: How I Replaced a $360/Month OpenSearch Cluster with S3 and In-Memory Search

I shelved a project in March 2025 because it cost $360/month to run.

I rebuilt it in January 2026 for $1.12/month.

Same functionality. Better architecture. No vector database.

It's a RAG pipeline — API Gateway → Lambda → Amazon Bedrock → S3 embeddings → in-memory cosine similarity search. It lives on my site and answers questions about my experience and work history in real time, grounded in structured data I built and curated myself.

The interesting parts:
— Why I killed OpenSearch after less than a week
— How in-memory search outperformed a network call at this scale
— The Anthropic/Bedrock access issue I still haven't fully resolved (Llama works fine)
— Why I handcrafted every knowledge base chunk instead of automating it
Full write-up: https://stephaniespanjian.com/blog/rag-cost-reduction-replaced-opensearch-s3-in-memory-search