Dev migrates agentic RAG app to AWS serverless, uncovers pre-existing data bugs

A developer completing a three-part series on migrating an agentic RAG assistant to AWS serverless infrastructure discovered two pre-existing bugs unrelated to the cloud move itself. A flawed chunk ID scheme caused 303 out of 24,775 document chunks to silently shadow each other during retrieval fusion, meaning some content could never surface in results. Separately, a 119 KB chunk — far exceeding the 8,192-token embedding model limit — would have failed or been silently truncated, leaving it absent from the vector index. The migration also required reworking a GitHub rate-limit handler, since sleeping inside AWS Lambda wastes billed compute time and risks hitting the 15-minute execution ceiling. Atomic budget reservation logic originally built on a single PostgreSQL UPDATE was successfully ported to a DynamoDB conditional write, preserving the concurrency-safe spending guarantee.