RAG (Retrieval-Augmented Generation) is the most effective pattern for a language model to answer accurately about your private data. Instead of expensive fine-tuning, you inject relevant context into each query. The model generates answers based on real facts from your documentation, not hallucinations.
But a RAG that works in a Jupyter notebook and a RAG that works in production with thousands of users are very different systems. This guide covers the architecture decisions that make the difference.
Step 1: Ingestion and intelligent chunking
Chunking is where most implementations fail. Splitting documents by a fixed number of tokens loses semantic context. We use recursive chunking that respects document structure: headings, sections, paragraphs. Each chunk carries metadata from the parent document, its relative position, and links to adjacent chunks.
For technical documents, the optimal size is usually between 500 and 1000 tokens with 10-15% overlap. But there is no universal rule — the right size depends on the type of queries your users make and the structure of your documents.
Step 2: Embeddings and vector storage
We convert each chunk into a high-dimensional vector using embedding models. The choice of model matters: larger models capture more semantic nuance but cost more and are slower.
The vector store (Pinecone, Weaviate, pgvector) is your knowledge database. Design the metadata schema from the start: you will need to filter by source, date, document type, and access permissions. Adding metadata later is expensive.
Step 3: Retrieval, re-ranking, and generation
Semantic search alone is not enough. A re-ranker (like Cohere Rerank or a cross-encoder) evaluates the actual relevance of each result in the context of the specific query. This dramatically improves precision, especially for ambiguous queries.
For generation, we use Claude with explicit instructions to cite sources. Each response includes references to the specific chunks that support it. If the model does not find enough information in the context, it must say so — an honest "I don't have data to answer" is more valuable than a convincing hallucination.
Evaluation: Measuring quality continuously
Without quantitative evaluation, you don't know if your RAG improves or degrades with each change. We measure retrieval precision (are the retrieved chunks relevant?), answer accuracy (is the answer correct?), and faithfulness (is the answer based on the chunks, not on model knowledge?).
We automate these evaluations with curated question sets and run them on every deploy.
